Summer is a great time to explore cool problems to keep your skills sharp!  Schedule a class today!

Contests & Programs AMC and other contests, summer programs, etc.
AMC and other contests, summer programs, etc.
3 M G
BBookmark  VNew Topic kLocked
Contests & Programs AMC and other contests, summer programs, etc.
AMC and other contests, summer programs, etc.
3 M G
BBookmark  VNew Topic kLocked
G
Topic
First Poster
Last Poster
k a May Highlights and 2025 AoPS Online Class Information
jlacosta   0
May 1, 2025
May is an exciting month! National MATHCOUNTS is the second week of May in Washington D.C. and our Founder, Richard Rusczyk will be presenting a seminar, Preparing Strong Math Students for College and Careers, on May 11th.

Are you interested in working towards MATHCOUNTS and don’t know where to start? We have you covered! If you have taken Prealgebra, then you are ready for MATHCOUNTS/AMC 8 Basics. Already aiming for State or National MATHCOUNTS and harder AMC 8 problems? Then our MATHCOUNTS/AMC 8 Advanced course is for you.

Summer camps are starting next month at the Virtual Campus in math and language arts that are 2 - to 4 - weeks in duration. Spaces are still available - don’t miss your chance to have an enriching summer experience. There are middle and high school competition math camps as well as Math Beasts camps that review key topics coupled with fun explorations covering areas such as graph theory (Math Beasts Camp 6), cryptography (Math Beasts Camp 7-8), and topology (Math Beasts Camp 8-9)!

Be sure to mark your calendars for the following upcoming events:
[list][*]May 9th, 4:30pm PT/7:30pm ET, Casework 2: Overwhelming Evidence — A Text Adventure, a game where participants will work together to navigate the map, solve puzzles, and win! All are welcome.
[*]May 19th, 4:30pm PT/7:30pm ET, What's Next After Beast Academy?, designed for students finishing Beast Academy and ready for Prealgebra 1.
[*]May 20th, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 1 Math Jam, Problems 1 to 4, join the Canada/USA Mathcamp staff for this exciting Math Jam, where they discuss solutions to Problems 1 to 4 of the 2025 Mathcamp Qualifying Quiz!
[*]May 21st, 4:00pm PT/7:00pm ET, Mathcamp 2025 Qualifying Quiz Part 2 Math Jam, Problems 5 and 6, Canada/USA Mathcamp staff will discuss solutions to Problems 5 and 6 of the 2025 Mathcamp Qualifying Quiz![/list]
Our full course list for upcoming classes is below:
All classes run 7:30pm-8:45pm ET/4:30pm - 5:45pm PT unless otherwise noted.

Introductory: Grades 5-10

Prealgebra 1 Self-Paced

Prealgebra 1
Tuesday, May 13 - Aug 26
Thursday, May 29 - Sep 11
Sunday, Jun 15 - Oct 12
Monday, Jun 30 - Oct 20
Wednesday, Jul 16 - Oct 29

Prealgebra 2 Self-Paced

Prealgebra 2
Wednesday, May 7 - Aug 20
Monday, Jun 2 - Sep 22
Sunday, Jun 29 - Oct 26
Friday, Jul 25 - Nov 21

Introduction to Algebra A Self-Paced

Introduction to Algebra A
Sunday, May 11 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Wednesday, May 14 - Aug 27
Friday, May 30 - Sep 26
Monday, Jun 2 - Sep 22
Sunday, Jun 15 - Oct 12
Thursday, Jun 26 - Oct 9
Tuesday, Jul 15 - Oct 28

Introduction to Counting & Probability Self-Paced

Introduction to Counting & Probability
Thursday, May 15 - Jul 31
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Wednesday, Jul 9 - Sep 24
Sunday, Jul 27 - Oct 19

Introduction to Number Theory
Friday, May 9 - Aug 1
Wednesday, May 21 - Aug 6
Monday, Jun 9 - Aug 25
Sunday, Jun 15 - Sep 14
Tuesday, Jul 15 - Sep 30

Introduction to Algebra B Self-Paced

Introduction to Algebra B
Tuesday, May 6 - Aug 19
Wednesday, Jun 4 - Sep 17
Sunday, Jun 22 - Oct 19
Friday, Jul 18 - Nov 14

Introduction to Geometry
Sunday, May 11 - Nov 9
Tuesday, May 20 - Oct 28
Monday, Jun 16 - Dec 8
Friday, Jun 20 - Jan 9
Sunday, Jun 29 - Jan 11
Monday, Jul 14 - Jan 19

Paradoxes and Infinity
Mon, Tue, Wed, & Thurs, Jul 14 - Jul 16 (meets every day of the week!)

Intermediate: Grades 8-12

Intermediate Algebra
Sunday, Jun 1 - Nov 23
Tuesday, Jun 10 - Nov 18
Wednesday, Jun 25 - Dec 10
Sunday, Jul 13 - Jan 18
Thursday, Jul 24 - Jan 22

Intermediate Counting & Probability
Wednesday, May 21 - Sep 17
Sunday, Jun 22 - Nov 2

Intermediate Number Theory
Sunday, Jun 1 - Aug 24
Wednesday, Jun 18 - Sep 3

Precalculus
Friday, May 16 - Oct 24
Sunday, Jun 1 - Nov 9
Monday, Jun 30 - Dec 8

Advanced: Grades 9-12

Olympiad Geometry
Tuesday, Jun 10 - Aug 26

Calculus
Tuesday, May 27 - Nov 11
Wednesday, Jun 25 - Dec 17

Group Theory
Thursday, Jun 12 - Sep 11

Contest Preparation: Grades 6-12

MATHCOUNTS/AMC 8 Basics
Friday, May 23 - Aug 15
Monday, Jun 2 - Aug 18
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

MATHCOUNTS/AMC 8 Advanced
Sunday, May 11 - Aug 10
Tuesday, May 27 - Aug 12
Wednesday, Jun 11 - Aug 27
Sunday, Jun 22 - Sep 21
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Problem Series
Friday, May 9 - Aug 1
Sunday, Jun 1 - Aug 24
Thursday, Jun 12 - Aug 28
Tuesday, Jun 17 - Sep 2
Sunday, Jun 22 - Sep 21 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Monday, Jun 23 - Sep 15
Tues & Thurs, Jul 8 - Aug 14 (meets twice a week!)

AMC 10 Final Fives
Sunday, May 11 - Jun 8
Tuesday, May 27 - Jun 17
Monday, Jun 30 - Jul 21

AMC 12 Problem Series
Tuesday, May 27 - Aug 12
Thursday, Jun 12 - Aug 28
Sunday, Jun 22 - Sep 21
Wednesday, Aug 6 - Oct 22

AMC 12 Final Fives
Sunday, May 18 - Jun 15

AIME Problem Series A
Thursday, May 22 - Jul 31

AIME Problem Series B
Sunday, Jun 22 - Sep 21

F=ma Problem Series
Wednesday, Jun 11 - Aug 27

WOOT Programs
Visit the pages linked for full schedule details for each of these programs!


MathWOOT Level 1
MathWOOT Level 2
ChemWOOT
CodeWOOT
PhysicsWOOT

Programming

Introduction to Programming with Python
Thursday, May 22 - Aug 7
Sunday, Jun 15 - Sep 14 (1:00 - 2:30 pm ET/10:00 - 11:30 am PT)
Tuesday, Jun 17 - Sep 2
Monday, Jun 30 - Sep 22

Intermediate Programming with Python
Sunday, Jun 1 - Aug 24
Monday, Jun 30 - Sep 22

USACO Bronze Problem Series
Tuesday, May 13 - Jul 29
Sunday, Jun 22 - Sep 1

Physics

Introduction to Physics
Wednesday, May 21 - Aug 6
Sunday, Jun 15 - Sep 14
Monday, Jun 23 - Sep 15

Physics 1: Mechanics
Thursday, May 22 - Oct 30
Monday, Jun 23 - Dec 15

Relativity
Mon, Tue, Wed & Thurs, Jun 23 - Jun 26 (meets every day of the week!)
0 replies
jlacosta
May 1, 2025
0 replies
4th grader qual JMO
HCM2001   50
N 9 minutes ago by steve4916
i mean.. whattttt??? just found out about this.. is he on aops? (i'm sure he is) where are you orz lol..
https://www.mathschool.com/blog/results/celebrating-success-douglas-zhang-is-rsm-s-youngest-usajmo-qualifier
50 replies
HCM2001
May 22, 2025
steve4916
9 minutes ago
24th PMO, Qualifying Stage #7
elpianista227   3
N 4 hours ago by BlackOctopus23
Suppose $a, b, c$ are the roots of the polynomial $x^3 + 2x^2 + 2$. Let $f$ be the unique monic polynomial whose roots are $a^2, b^2, c^2$. Find $f(1)$.
3 replies
elpianista227
Yesterday at 5:20 AM
BlackOctopus23
4 hours ago
Find the Angle Measure
4everwise   4
N 4 hours ago by Rabbit47
An acute isosceles triangle, $ABC$ is inscribed in a circle. Through $B$ and $C$, tangents to the circle are drawn, meeting at point $D$. If $\angle ABC=\angle ACB=2\angle D$ and $x$ is the radian measure of $\angle A$, then $x=$

IMAGE

$\text{(A)} \ \frac37\pi \qquad \text{(B)} \ \frac49\pi \qquad \text{(C)} \ \frac5{11}\pi \qquad \text{(D)} \ \frac6{13}\pi \qquad \text{(E)} \ \frac7{15}\pi$
4 replies
4everwise
Apr 4, 2006
Rabbit47
4 hours ago
[Sipnayan 2023 JHS] Written Round, Easy, #3:
LilKirb   2
N 4 hours ago by BlackOctopus23
Let $\alpha,$ $\beta,$ $\gamma,$ be the real roots of
\[x^3 + 7x^2 -6x - 13 = 0\]Find $\alpha^2 + \beta^2 + \gamma^2$
2 replies
LilKirb
Yesterday at 2:43 PM
BlackOctopus23
4 hours ago
An Ineq.
Cirno-fumofumo   1
N 6 hours ago by Marrelia
For any a>0,x>0,prove that 1<(sqrt(1/(1+x)))+(sqrt(1/(1+a)))+sqrt(ax/(ax+8))<2
(I'm a beginner,so I don't know how to use latex…)
1 reply
Cirno-fumofumo
Yesterday at 1:08 PM
Marrelia
6 hours ago
Pertenacious Polynomial Problem
BadAtCompetitionMath21420   8
N Yesterday at 7:31 PM by BadAtCompetitionMath21420
Let the polynomial $P(x) = x^3-x^2+px-q$ have real roots and real coefficients with $q>0$. What is the maximum value of $p+q$?

This is a problem I made for my math competition, and I wanted to see if someone would double-check my work (No Mike allowed):

solution
Is this solution good?
8 replies
BadAtCompetitionMath21420
May 17, 2025
BadAtCompetitionMath21420
Yesterday at 7:31 PM
NT problem
toanrathay   1
N Yesterday at 5:24 PM by orange0707
Let $p$ be a prime and $m,n$ be positive integers such that $m>1$ and $\dfrac{m^{pn}-1}{m^n-1}$ is prime. Prove that $pn\mid (p-1)^n+1.$
1 reply
toanrathay
Friday at 11:57 AM
orange0707
Yesterday at 5:24 PM
not obvious trig identity!
mathmax001   2
N Yesterday at 5:19 PM by mathmax001
Problem ( trigonometry )
Let $ x \in \mathbb{R} $ and n a positive integer $ n >=1 $, Show that : $$ \tan\left({\frac{(n+1)x}{2}}\right)= \frac{\sum_{k=1}^n{\sin kx}}{\sum_{k=1}^n{\cos kx}} $$
Here is my take in this video: https://youtu.be/DBPyHNqk0GI?si=9r-YDuwv794AGe1p
2 replies
mathmax001
Yesterday at 1:43 AM
mathmax001
Yesterday at 5:19 PM
confused
greenplanet2050   4
N Yesterday at 4:17 PM by greenplanet2050
um something weird happened today

I was doing the 2002 aime ii and i tried #9

I used PIE with $(2^{10}-1)-(\text{Number of times there are n same elements})$

so for like 1 same element i did $2^9 \cdot \dbinom{10}{1}$ cause there are 10 ways to choose 1 element that will be repeated. Similarly for 2 same elements it would be $2^8 \cdot \dbinom{10}{2}$

So if $A_n=2^{10-n} \cdot \dbinom{10}{n},$ the answer would be $(2^{10}-1)-([A_1+A_3+A_5+A_7+A_9]-[A_2+A_4+A_6+A_8+A_{10}].$ But this number turned out to be $0.$

Later when looking at the solution, i found out that the correct number was $28501.$ But I realized that $A_2+A_4+A_6+A_8+A_{10}=28501.$ So I was really confused of why i got the right answer somehow in my calculations.

Can someone explain why this happened? Thanks! :)
4 replies
greenplanet2050
Friday at 6:29 PM
greenplanet2050
Yesterday at 4:17 PM
[15th PMO] National Orals, Part 1, #9
LilKirb   1
N Yesterday at 4:09 PM by pingpongmerrily
If $x^2+2x+5$ is a factor of $x^4 +ax^2 + b$, find the sum of $a+b.$
1 reply
LilKirb
Yesterday at 4:04 PM
pingpongmerrily
Yesterday at 4:09 PM
Inequalitis
sqing   1
N Yesterday at 3:55 PM by DAVROS
Let $ a,b,c\geq  0 , a^2+b^2+c^2 =3.$ Prove that
$$a^3 +b^3 +c^3 +\frac{11}{5}abc  \leq \frac{26}{5}$$
1 reply
sqing
Yesterday at 2:44 AM
DAVROS
Yesterday at 3:55 PM
AIME qual outside US?
daijobu   10
N Yesterday at 5:23 AM by Yiyj
Can students outside the US take the AIME if they earn a qualifying score?
10 replies
daijobu
Friday at 7:10 PM
Yiyj
Yesterday at 5:23 AM
[$10K+ IN PRIZES] Poolesville Math Tournament (PVMT) 2025
qwerty123456asdfgzxcvb   20
N Yesterday at 2:13 AM by panda2018
Hi everyone!

After the resounding success of the first three years of PVMT, the Poolesville High School Math Team is excited to announce the fourth annual Poolesville High School Math Tournament (PVMT)! The PVMT team includes a MOPper and multiple USA(J)MO and AIME qualifiers!

PVMT is open to all 6th-9th graders in the country (including rising 10th graders). Students will compete in teams of up to 4 people, and each participant will take three subject tests as well as the team round. The contest is completely free, and will be held virtually on June 7, 2025, from 10:00 AM to 4:00 PM (EST).

Additionally, thanks to our sponsors, we will be awarding approximately $10K+ worth of prizes (including gift cards, Citadel merch, AoPS coupons, Wolfram licenses) to top teams and individuals. More details regarding the actual prizes will be released as we get closer to the competition date.

Further, newly for this year we might run some interesting mini-events, which we will announce closer to the competition date, such as potentially a puzzle hunt and integration bee!

If you would like to register for the competition, the registration form can be found at https://pvmt.org/register.html or https://tinyurl.com/PVMT25.

Additionally, more information about PVMT can be found at https://pvmt.org

If you have any questions not answered in the below FAQ, feel free to ask in this thread or email us at falconsdomath@gmail.com!

We look forward to your participation!

FAQ
20 replies
qwerty123456asdfgzxcvb
Apr 5, 2025
panda2018
Yesterday at 2:13 AM
Expression is a Cube
nosaj   38
N Yesterday at 1:42 AM by NicoN9
Source: 2015 AIME I Problem 3
There is a prime number $p$ such that $16p+1$ is the cube of a positive integer. Find $p$.
38 replies
nosaj
Mar 20, 2015
NicoN9
Yesterday at 1:42 AM
complex number geo
zhoujef000   32
N Apr 18, 2025 by Jaxman8
Source: 2025 AIME I #8
Let $k$ be a real number such that the system \begin{align*} &|25+20i-z|=5\\ &|z-4-k|=|z-3i-k| \\ \end{align*}has exactly one complex solution $z.$ The sum of all possible values of $k$ can be written as $\dfrac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n.$ Here $i=\sqrt{-1}.$
32 replies
zhoujef000
Feb 7, 2025
Jaxman8
Apr 18, 2025
complex number geo
G H J
G H BBookmark kLocked kLocked NReply
Source: 2025 AIME I #8
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
zhoujef000
322 posts
#1 • 1 Y
Y by mathfan2020
Let $k$ be a real number such that the system \begin{align*} &|25+20i-z|=5\\ &|z-4-k|=|z-3i-k| \\ \end{align*}has exactly one complex solution $z.$ The sum of all possible values of $k$ can be written as $\dfrac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n.$ Here $i=\sqrt{-1}.$
This post has been edited 1 time. Last edited by zhoujef000, Feb 8, 2025, 5:44 PM
Reason: think this was how it was aligned on the test
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
MathXplorer10
163 posts
#2
Y by
I got 73/4 —> 77
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
plang2008
337 posts
#3 • 4 Y
Y by bjump, AtharvNaphade, Roots_Of_Moksha, chess12500
First equation is circle with center $(25, 20)$ and radius $5$, second equation is perpendicular bisector of line through $(4+k, 0)$ and $(k, 3)$. This is $y - 1.5 = \frac 43 (x - (2 + k))$. Now notice we want this line to be tangent to the circle. There are two such lines, symmetric across $(25,20)$. Plugging this point in gives $k = \frac{73}{8}$ so the answer is $\frac{73}{4} \implies \boxed{077}$.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
KenWuMath
58 posts
#4 • 9 Y
Y by bjump, AlexWin0806, OlympusHero, MathPerson12321, roribaki, EpicBird08, ihatemath123, Sedro, aidan0626
i forgor the geometric interpretation :blush:
and did perhaps the ugliest bash of my life
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
ninjaforce
96 posts
#5
Y by
Clean solution that requires next to no insight
This post has been edited 1 time. Last edited by ninjaforce, Feb 11, 2025, 6:18 AM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
exp-ipi-1
1074 posts
#6
Y by
Who else though the circle is centered at (25,-20) and put 317
This post has been edited 1 time. Last edited by exp-ipi-1, Feb 7, 2025, 4:01 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
OlympusHero
17020 posts
#7 • 1 Y
Y by razormouth
I put 73/8 after bashing for 20 min
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Elephant200
1472 posts
#8
Y by
I got the insight but then I totally screwed up after that :(
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
EaZ_Shadow
1291 posts
#9 • 1 Y
Y by Ad112358
Elephant200 wrote:
I got the insight but then I totally screwed up after that :(

same :(
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
xHypotenuse
788 posts
#10
Y by
This bash took me 30 MINUTES

stupid vietabash

still got it right -> 73/4 -> 77.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Bluesoul
899 posts
#11
Y by
Let $z=x+yi, (x-(4+k))^2+y^2=(x-k)^2+(y-3)^2$, which simplifies to $8x-6y-8k-7=0$

Now we want this line's distance to $(25,20)$ is $5$ since the first expression is a circle centered at $(25,20)$ with radius $5$, so $\frac{|73-8k|}{10}=5, k=\frac{23}{8}, \frac{123}{8}$, sum up to $\frac{73}{4}\implies \boxed{077}$
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
GrantStar
821 posts
#12 • 2 Y
Y by sami1618, remedy
Oops I forgot to subtract 4 :sob:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
williamxiao
2517 posts
#13
Y by
Didn’t simplify the fraction , put 154 :)

The key idea is to interpret the problem geometrically. The first equation says that z lies on a circle with radius 5 centered at $(25,20)$ and the second equation says that z lies on the perpendicular bisector of (k+4,0) and (k,3). The perpendicular bisector of this line has slope 4/3. We want only one solution for z, so we are simply looking for the lines tangent to the circle with slope 4/3. Once we have these two lines, it must pass through $(k+2, \frac{3}{2})$. Solve and sum the values of k to get $\frac{146}{8}$ (:sob:) $=\frac{73}{4} \rightarrow \boxed{77}$
This post has been edited 1 time. Last edited by williamxiao, Feb 7, 2025, 6:13 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Math4Life7
1703 posts
#14
Y by
don't enjoy the amount of computation in this problem
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
cappucher
99 posts
#15 • 2 Y
Y by anduran, ninjaforce
Bashing time

Let $z = a + bi$. Then our equations become

\[(25 - a)^2 + (20 - b)^2 = 25\]\[(a - 4 - k)^2 + b^2 = (a - k)^2 + (b - 3)^2\]
We expand out the second equation:

\[a^2 + 16 + k^2 - 8a - 2ak + 8k + b^2 = a^2 - 2ak + k^2 + b^2 - 6b + 9\]\[16 - 8a  + 8k = -6b + 9\]\[a = \frac{8k + 7 + 6b}{8}\]
We now plug this into the first equation:

\[\left(25 - \frac{8k + 7 + 6b}{8}\right)^2 + (20 - b)^2 = 25\]\[\left(\frac{193}{8} - k - \frac{3}{4}b\right)^2 + (20 - b)^2 = 25\]
Let $v = \frac{193}{8} - k$ to simplify calculations.

\[\left(v - \frac{3}{4}b\right)^2 + (20 - b)^2 = 25\]\[v^2 - \frac{3}{2}bv + \frac{9}{16}b^2 + 400 - 40b + b^2 = 25\]\[\frac{25}{16}b^2 - b\left(\frac{3}{2}v + 40\right) + (v^2 + 375)\]
In order for there to be exactly one solution for $z$, the discriminant of this quadratic must be $0$:

\[\left(\frac{3}{2}v + 40\right)^2 - 4\left(\frac{25}{16}\right)\left(v^2 + 375\right) = 0\]
Since we are asked for the sum of all $k$, we just use Vieta's relations on this quadratic.

\[\frac{9}{4}v^2 + 120v + 1600 - \frac{25}{4}v^2 - 4\left(\frac{25}{16}\right)\left(375\right) = 0\]\[-4v^2 + 120v + c = 0\]
We can ignore the constant term because it's irrelevant to the sum of the roots. Since we have $v_1 + v_2 = 30$, we conclude that

\[2\left(\frac{193}{8}\right) - (k_1 + k_2) = 30\]\[k_1 + k_2 = \frac{73}{4}\]
So the answer is $73 + 4 = \boxed{77}$.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
BS2012
1058 posts
#16
Y by
Algebraic non-bash solution

The first equation implies
$$z-k=(25-5\cos(a)-k)+(20-5\sin(a))i$$for some real $a.$ Then, let $z-k=x+yi.$ By the second equation,
$$(x-4)^2+y^2=x^2+(y-3)^2$$which simplifies to
$$8x=6y+7.$$Plugging in the real parts for $x$ and $y,$ we have
$$200-40\cos(a)-8k=127+7-30\sin(a).$$This means that
$$73-8k=40\cos(a)-30\sin(a).$$Dividing both sides by $50,$ we have
$$\dfrac{73-8k}{50}=\dfrac{4}{5}\cos(a)-\dfrac{3}{5}\sin(a).$$Let $m$ be an angle such that $\cos(m)=\frac{4}{5}$ and $\sin(m)=\frac{3}{5}.$ Recognizing the cosine angle addition formula, we have
$$\dfrac{73-8k}{50}=\cos(a+m).$$This has one solution for $a$ precisely when
$$\dfrac{73-8k}{50}=\pm 1,$$and simple algebra gets the answer
$$k=\dfrac{73\pm 50}{8}\implies \dfrac{73-50+73+50}{8}=\dfrac{73}{4}\implies\boxed{077}.$$
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Iwowowl253
144 posts
#17
Y by
Rip, i put $146+8=154$
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
newhydepark
10 posts
#18
Y by
You can use calculus to solve this problem.
If we let $z=a+bi$, expanding/simplifying the system, we get
$$(25-a)^2+(20-b)^2=25$$$$-8a+8k+6b+7=0$$It's worthwhile to note, this boils down to observing where a tangent line occurs on the circle with slope $\frac{4}{3}$. If we let $25-a=x$ and $20-b=y$, using implicit differentiation on the circle, we get
$$ 2x + 2y (y') = 0 $$Solving for $y'$, we get
$$ \frac{dy}{dx} = \frac{-x}{y} = \frac{4}{3}$$If we substitute the derivative into the circle equation, we will get the solutions $(x,y) = (-4,3)$ and $(4,-3)$. Do not forget we sub $x$ and $y$ for $a$ and $b$, so the points $(a,b)$ are $(29,17)$ and $(21, 23)$. If we plug it into the tangent line equation, and solve for $k$ for both, we get
$$ \frac{8(50)-6(40)-14}{8} = \frac{146}{8} = \frac{73}{4} => 73 + 4 = \boxed{077} $$
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
xTimmyG
265 posts
#19
Y by
this problem almost cooked my score :wallbash_red:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
megarnie
5611 posts
#20
Y by
Bash is not bad, especially if you eliminate fractions

Let $z = a + bi$. We have $(a-25)^2 + (b-20)^2 = 25$ and $(a - 4 - k)^2 + b^2 = (a - k)^2 + (b - 3)^2$.

The second equation can be easily simplified (through expansion or difference of squares) as \[ 6b = 8a - (8k + 7) \]
Now let $x = 8k + 7$.

The first equation becomes $a^2 - 50a + b^2 - 40b  + 1000 = 0$, or \[ 36a^2 - 1800a + (6b)^2 - 240(6b) + 36000 = 0 \]
Setting $6b = 8a - x$ gives that the LHS is equal to \[ 36a^2 - 1800a + (8a)^2 - 16xa + x^2 - 1920a + 240x + 36000\]
This can be rewritten as \[ 100a^2 - (16x + 3720) a + x^2 + 240x + 36000\]There is one solution iff the discriminant is $0$, so $x$ works iff \[ (16x + 3720)^2 = 400(x^2 + 240x + 36000),\]or \[ (4x + 930)^2 = 25(x^2 + 240x + 36000)\]If $x$ is an integer divisible by $4$, then taking modulo $8$ gives a contradiction. Thus, if $x$ is an integer, $4\nmid x$.

The sum of the roots (counting double roots twice) of this is just $\frac{8 \cdot 930 - 25 \cdot 240 }{9} = \frac{8 \cdot 310 - 25 \cdot 80}{3} = 160$. Since $4$ doesn't divide any root, there is not a double root, and therefore the sum of all possible values of $k$ is just \[ \frac{160 - 2 \cdot 7}{8} = \frac{73}{4} \implies \boxed{077} \]
(note: one can also just compute the roots to be $30$ and $130$)
This post has been edited 1 time. Last edited by megarnie, Feb 7, 2025, 10:40 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Mr.Sharkman
501 posts
#21
Y by
Bruh $x= a+bi,$ then $(a-(4+k))^{2}+b^{2} = (a-k)^{2}+(b-3i)^{2},$ which becomes $8k+7 = 8a-6b.$ Then, $c = 20-a,$ $d = 20-d,$ and then $8k+7 =80-8c+6d,$ and $(-8c+6d)^{2} \le (8^{2}+6^{2})(25)$ by Cauchy, then $-50 \le -8c+6d \le 50,$ so $30 \le 8k+7 \le 130,$ giving a final answer of $\frac{73}{4} \implies \boxed{073}.$

EDIT: yeah I got $77.$ Typo lol
This post has been edited 1 time. Last edited by Mr.Sharkman, Feb 21, 2025, 1:58 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
RedFireTruck
4243 posts
#22 • 1 Y
Y by bjump
The perpendicular bisector of $(k+4,0)$ and $(k,3)$ is $8x-6y=8k+7$.

Note that $8(25)-6(20)=80$.

Therefore, we want $\frac{|8k+7-80|}{\sqrt{8^2+6^2}}=5$, or $|8k-73|=50$.

Therefore, the sum of all possible values of $k$ is $\frac{73}{8}\cdot 2=\frac{73}4$ and the answer is $73+4=\boxed{077}$.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Happyllamaalways
478 posts
#23
Y by
Anyone else did this with calculus? :skull:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
lovematch13
671 posts
#24
Y by
I accidently multiplied by $2$ again and got $\dfrac{73}{2}$ :sob:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
ilikemath247365
267 posts
#25
Y by
cappucher wrote:
Bashing time

Let $z = a + bi$. Then our equations become

\[(25 - a)^2 + (20 - b)^2 = 25\]\[(a - 4 - k)^2 + b^2 = (a - k)^2 + (b - 3)^2\]
We expand out the second equation:

\[a^2 + 16 + k^2 - 8a - 2ak + 8k + b^2 = a^2 - 2ak + k^2 + b^2 - 6b + 9\]\[16 - 8a  + 8k = -6b + 9\]\[a = \frac{8k + 7 + 6b}{8}\]
We now plug this into the first equation:

\[\left(25 - \frac{8k + 7 + 6b}{8}\right)^2 + (20 - b)^2 = 25\]\[\left(\frac{193}{8} - k - \frac{3}{4}b\right)^2 + (20 - b)^2 = 25\]
Let $v = \frac{193}{8} - k$ to simplify calculations.

\[\left(v - \frac{3}{4}b\right)^2 + (20 - b)^2 = 25\]\[v^2 - \frac{3}{2}bv + \frac{9}{16}b^2 + 400 - 40b + b^2 = 25\]\[\frac{25}{16}b^2 - b\left(\frac{3}{2}v + 40\right) + (v^2 + 375)\]
In order for there to be exactly one solution for $z$, the discriminant of this quadratic must be $0$:

\[\left(\frac{3}{2}v + 40\right)^2 - 4\left(\frac{25}{16}\right)\left(v^2 + 375\right) = 0\]
Since we are asked for the sum of all $k$, we just use Vieta's relations on this quadratic.

\[\frac{9}{4}v^2 + 120v + 1600 - \frac{25}{4}v^2 - 4\left(\frac{25}{16}\right)\left(375\right) = 0\]\[-4v^2 + 120v + c = 0\]
We can ignore the constant term because it's irrelevant to the sum of the roots. Since we have $v_1 + v_2 = 30$, we conclude that

\[2\left(\frac{193}{8}\right) - (k_1 + k_2) = 30\]\[k_1 + k_2 = \frac{73}{4}\]
So the answer is $73 + 4 = \boxed{77}$.

Tried to do this, still failed, and put 73/8 :sob:
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Antonyliao
15 posts
#26
Y by
Different solution:

we first let $z = a+bi$ and ignore k. Then $|(a-4)+bi|=|a+(b-3)i| \Rightarrow b=\frac{4}{3}a-\frac{7}{6}$. Now let's consider an a-b plane. $|25+20i-z|=5$ is another way of saying that a point on the line $-z$, transformed 25 units to the right and 20 units up, lies on the circle with radius 5 centered at the origin. Since $-z$ is linear, the fact that there is only one and only one solution to $z$ means that the line $-z$ is tangent to the circle. But $-z$ is the graph of $z$ rotated around the origin by 180 degrees, so $-z$ also has slope $\frac43$. Thus, the tangency points are $(-4,3)$ and$ (4,-3)$. transform these points back to their original positions, and we get $(-29,-17)$ and $(-21,23)$. But the a-coordinates of the intersection of $-z=\frac43a+\frac76$ with $y=-17$ and $y=-23$ is $-\frac{109}8, -\frac{145}8$, which is a contradiction. Now let's consider k. The added $-k$ in $|z-4-k|=|z-3i-k|$ means that $-z$ is moved $k$ units to the left. thus, $k =-\frac{145}8 + 23$ or $-\frac{109}8 + 17$, which gives $k_1=\frac{23}8$, $k_2=\frac{123}8 \Rightarrow k_1+k_2=\frac{73}4 \Rightarrow$ the answer is $73 + 4 = \boxed{077}$.


In this graph, $k_1=A'D$, $k_2=B'C$.
Attachments:
This post has been edited 1 time. Last edited by Antonyliao, Feb 9, 2025, 12:09 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
sadas123
1330 posts
#27
Y by
Happyllamaalways wrote:
Anyone else did this with calculus? :skull:

Nope but I spent to much time but got the answer of $\boxed{077}$
This post has been edited 2 times. Last edited by sadas123, Feb 9, 2025, 10:08 PM
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
jasperE3
11395 posts
#28
Y by
zhoujef000 wrote:
Let $k$ be a real number such that the system \begin{align*} |25+20i-z|&=5\\ |z-4-k|&=|z-3i-k| \\ \end{align*}has exactly one complex solution $z.$ The sum of all possible values of $k$ can be written as $\dfrac{m}{n},$ where $m$ and $n$ are relatively prime positive integers. Find $m+n.$ Here $i=\sqrt{-1}.$

Write $z=x+yi$. We have:
$$5^2=|(25-x)+(20-y)i|^2=(25-x)^2+(20-y)^2=(x-25)^2+(y-20)^2$$and
$$|(x-4-k)+yi|^2=|(x-k)+(y-3)i|^2\Rightarrow(x-4-k)^2+y^2=(x-k)^2+(y-3)^2.$$Rearranging the second equation, we have $y=\frac43x-\frac{8k+7}6$.
-8k-7)/6

The equation $(x-25)^2+(y-20)^2=5^2$ can be interpreted geometrically to mean that $(x,y)$ lies on a circle in the Cartesian plane with center $(25,20)$ and radius $5$, while the equation $y=\frac43x-\frac43k-\frac76$ can be interpreted to mean that $(x,y)$ lies on a line in the Cartesian plane with slope $\frac43$ and a height that is based on $k$.

For this system to have exactly one solution, the line must intersect the circle at exactly one point, i.e. the line must be tangent to the circle.

Solution 1:
The radius that intersects the point of tangency must then be perpendicular to the line $y=\frac43x-\frac43k-\frac76$, so it must have slope $-\frac34$. Since the radius goes through the center of the circle, it lies on $y=-\frac34x+\frac{155}4$. The intersection of the line $y=-\frac34x+\frac{155}4$ with the circle yields the two possible points of tangency. To find these, we substitute into the equation of the circle:
\begin{align*}
(x-25)^2+\left(-\frac34x+\frac{155}4-20\right)^2&=25\\
(4x-100)^2+(-3x+75)^2&=400\\
16x^2-800x+10000+9x^2-450x+5625&=400\\
x^2-50x+609&=0\\
x&=25\pm4\\
y&=-\frac34x+\frac{155}4=20\mp3
\end{align*}Therefore, after rearranging $y=\frac43x-\frac43k-\frac76$ into $k=x-\frac34y-\frac78$, we get that $k$ is either:
$$k=29-\frac34\cdot17-\frac78=\frac{123}8$$or
$$k=21-\frac34\cdot23-\frac78=\frac{23}8$$so the sum of these is $\frac{146}8=\frac{73}4\Rightarrow\boxed{077}$.
alternate finish
[asy]
import graph;

size(400);
real r = 5;

draw((0,0)--(50,0), Arrow);
draw((0,0)--(0,40), Arrow);

label("$x$", (50, 0), NE);
label("$y$", (0, 40), NE);

draw(Circle((25,20), r));
dot((25,20));
label(scale(0.9)*"$(25,20)$", (25,20), NNE);

draw((3,36.5)--(47,3.5),Arrows);
label("$y=-\frac34x+\frac{155}4$",(46,4.25),NE);

dot((29,17));
label(scale(0.9)*"$(29,17)$",(25+4*r/5,-3*r/5+20),E);
dot((21,23));
label(scale(0.9)*"$(21,23)$",(25-4*r/5,3*r/5+20),W);

draw((6,3)--(31.5,37),Arrows);
label(scale(0.9)*"$k=\frac{23}8$",(31.5,37),NE);
draw((18.5,3)--(37,83/3),Arrows);
label(scale(0.9)*"$k=\frac{123}8$",(37,83/3),NE);

label(scale(0.9)*"$y=\frac43x-\frac43k-\frac76$",(12.27,3));
[/asy]

Solution 2:
Let the two possible points of tangency on the circle be $(x_1,y_1)$ and $(x_2,y_2)$. Note that the midpoint of these is the center of the circle, $(25,20)$, so $\left(\frac{x_1+y_1}2,\frac{x_2+y_2}2\right)=(25,20)$, that is, $x_1+x_2=50$ and $y_1+y_2=40$. Then the sum of the possible values for $k$ will be:
\begin{align*}
k_1+k_2&=x_1-\frac34y_1-\frac78+x_2-\frac34y_2-\frac78\\
&=(x_1+x_2)-\frac34(y_1+y_2)-\frac74\\
&=\frac{73}4\Rightarrow\boxed{077}
\end{align*}
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
dragoon
1947 posts
#29
Y by
Wait I got 68/9, I think I got really lucky lol
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Jaxman8
124 posts
#31
Y by
I got 73/4, and also got 077 for q10 so I changed changed my answer.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Gapple
1 post
#32
Y by
Let $z = x + yi$, and the system can be transformed into this:

$$
\begin{cases}
x^2 + y^2 - 50x - 40y + 1000 = 0 \\
y = \dfrac{4}{3} x - \dfrac{8k + 7}{6}
\end{cases}
$$
It has 1 solution, so we want the line to be tangent to the circle, so we get $(x, y) = (21, 23), (29, 17)$. Plugging these into the second equation, and we get $k_1 = 23/8, k_2 = 123/8$. So the answer is $k_1 + k_2 = 146/8 = 73/4 \implies \boxed{77}$.
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
MathRook7817
751 posts
#33
Y by
orz question
Z K Y
The post below has been deleted. Click to close.
This post has been deleted. Click here to see post.
Jaxman8
124 posts
#34
Y by
I have no idea how I got this question right in the first place, but when I got #10 as 077 aswell I changed my answer to 047 on #8 bc I got that before.
Z K Y
N Quick Reply
G
H
=
a