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k a March Highlights and 2025 AoPS Online Class Information
jlacosta   0
Mar 2, 2025
March is the month for State MATHCOUNTS competitions! Kudos to everyone who participated in their local chapter competitions and best of luck to all going to State! Join us on March 11th for a Math Jam devoted to our favorite Chapter competition problems! Are you interested in training for MATHCOUNTS? Be sure to check out our AMC 8/MATHCOUNTS Basics and Advanced courses.

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Do you have plans this summer? There are so many options to fit your schedule and goals whether attending a summer camp or taking online classes, it can be a great break from the routine of the school year. Check out our summer courses at AoPS Online, or if you want a math or language arts class that doesn’t have homework, but is an enriching summer experience, our AoPS Virtual Campus summer camps may be just the ticket! We are expanding our locations for our AoPS Academies across the country with 15 locations so far and new campuses opening in Saratoga CA, Johns Creek GA, and the Upper West Side NY. Check out this page for summer camp information.

Be sure to mark your calendars for the following events:
[list][*]March 5th (Wednesday), 4:30pm PT/7:30pm ET, HCSSiM Math Jam 2025. Amber Verser, Assistant Director of the Hampshire College Summer Studies in Mathematics, will host an information session about HCSSiM, a summer program for high school students.
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0 replies
jlacosta
Mar 2, 2025
0 replies
Reflections
junlongsun   5
N 23 minutes ago by junlongsun
2024 State S25:
A beetle starts at the point with coordinates (8, 5), travels to a point on the line
y = 2, then to some point on the line y = x, and then finally travels to the point
with coordinates (5, 4). One possible path that the beetle might follow is shown.
What is the length of the shortest possible path
that the beetle could take? Express your answer
in simplest radical form

I've heard people talking about reflecting over y=x and y=2, how does that work?
5 replies
junlongsun
2 hours ago
junlongsun
23 minutes ago
Geometric problem
Notsurefornoworever   0
43 minutes ago
Let ABC be a right triangle with a right angle BCA. Let CD be the altitude from vertex C to AB. Prove that the distances from the point D to the legs is proportional to the lengths of the legs.
0 replies
Notsurefornoworever
43 minutes ago
0 replies
Sequence interesting problem
vickyricky   10
N an hour ago by kamatadu
Let $ a_{0} =1$ and $ b_{0} =1$ . Define $a_{n} , b_{n} $ for $ n\ge 1$ as $a_{n}=a_{n-1}+2b_{n-1} $ , $b_{n}=a_{n-1}+b_{n-1} $ . Prove that $\lim_{n\to\infty}\frac{a_n}{b_n}$ exists and find it's value .
10 replies
vickyricky
Jun 6, 2020
kamatadu
an hour ago
Very nice Darboux epsilon-delta
CatalinBordea   1
N an hour ago by QQQ43
Source: Romanian National Olympiad 2000, Grade XI, Problem 4
Let $ f:\mathbb{R}\longrightarrow\mathbb{R} $ be a function that satisfies the conditions:
$ \text{(i)}\quad \lim_{x\to\infty} (f\circ f) (x) =\infty =-\lim_{x\to -\infty} (f\circ f) (x) $
$ \text{(ii)}\quad f $ has Darboux’s property

a) Prove that the limits of $ f $ at $ \pm\infty $ exist.
b) Is possible for the limits from a) to be finite?
1 reply
CatalinBordea
Oct 2, 2018
QQQ43
an hour ago
k mathcounts advice pls
muuheng   3
N an hour ago by aoh11
hi i have around 9 days until my state round competition, and my chapter score was 32. My state isn't that competitive, so i think the cutoff for nats last year was like 31, and i scored second in my chapter but i'm from a less competitive chapter. I think tenth place this year for the most competitive chapter in my state got 34? (as well as 11th thru maybe 20th place). So can anyone whose like orz give me like advice on how to lock in 9 days so maybe i can make it to state top 10 or maybe even nationals (i'm only hoping for top 10 but any help is appreciated :love: ). also anyone wanna guess my state for fun. and maybe if you've taken the state yet tell me how it went pretty pls
3 replies
muuheng
Today at 5:45 AM
aoh11
an hour ago
My MATHCOUNTS journey + I need advice
nitride   22
N an hour ago by aoh11
So I don't really care if I dox myself but I went to one of the single worst chapters in all of Florida, the Indian river chapter(even the runner of mathcounts states was sayin we would lose to osprey in states). I don't exactly know what my score is, but all I know is that I got 1st place sprint and chapter but then sold CD. If I had to guess, my score was around the 30-37 range. I also mocked at around a 70 on amc 10. My questions are:
1.
What are my chances of me getting nats qual
2.
Should I study the day before the competition
22 replies
nitride
Today at 1:36 AM
aoh11
an hour ago
Most Evil and Brutal Integral Ever Officially Proposed for an Integration Bee
Silver08   3
N 2 hours ago by Silver08
Source: UK University Integration Bee 2024-2025 Round 2 Relay (Singapore)
Compute: \[ \int_{1}^{2}e^{x( x+\sqrt{x^2-1} )}dx \]
3 replies
Silver08
Mar 6, 2025
Silver08
2 hours ago
IMC 2018 P4
ThE-dArK-lOrD   17
N 4 hours ago by sangsidhya
Source: IMC 2018 P4
Find all differentiable functions $f:(0,\infty) \to \mathbb{R}$ such that
$$f(b)-f(a)=(b-a)f’(\sqrt{ab}) \qquad \text{for all}\qquad a,b>0.$$
Proposed by Orif Ibrogimov, National University of Uzbekistan
17 replies
ThE-dArK-lOrD
Jul 24, 2018
sangsidhya
4 hours ago
f(x)=x-xe^(-1/x)
Sayan   6
N 4 hours ago by kamatadu
Source: ISI (BS) 2006 #6
(a) Let $f(x)=x-xe^{-\frac1x}, \ \ x>0$. Show that $f(x)$ is an increasing function on $(0,\infty)$, and $\lim_{x\to\infty} f(x)=1$.

(b) Using part (a) or otherwise, draw graphs of $y=x-1, y=x, y=x+1$, and $y=xe^{-\frac{1}{|x|}}$ for $-\infty<x<\infty$ using the same $X$ and $Y$ axes.
6 replies
Sayan
Jun 2, 2012
kamatadu
4 hours ago
Square of a rational matrix of dimension 2
loup blanc   7
N Today at 11:53 AM by ysharifi
The following exercise was posted -two months ago- on the Website StackExchange; cf.
https://math.stackexchange.com/questions/5006488/image-of-the-squaring-function-on-mathcalm-2-mathbbq
There was no solution on Stack.

-Statement of the exercise-
We consider the matrix function $f:X\in M_2(\mathbb{Q})\mapsto X^2\in M_2(\mathbb{Q})$.
Find the image of $f$.
In other words, give a method to decide whether a given matrix has or does not have at least a square root
in $M_2(\mathbb{Q})$; if the answer is yes, then give a method to calculate at least one of its roots.
7 replies
loup blanc
Feb 17, 2025
ysharifi
Today at 11:53 AM
find the isomorphism
nguyenalex   10
N Today at 11:38 AM by Royrik123456
I have the following exercise:

Let $E$ be an algebraic extension of $K$, and let $F$ be an algebraic closure of $K$ containing $E$. Prove that if $\sigma : E \to F$ is an embedding such that $\sigma(c) = c$ for all $c \in K$, then $\sigma$ extends to an automorphism of $F$.

My attempt:

Theorem (*): Suppose that $E$ is an algebraic extension of the field $K$, $F$ is an algebraically closed field, and $\sigma: K \to F$ is an embedding. Then, there exists an embedding $\tau: E \to F$ that extends $\sigma$. Moreover, if $E$ is an algebraic closure of $K$ and $F$ is an algebraic extension of $\sigma(K)$, then $\tau$ is an isomorphism.

Back to our main problem:

Since $K \subset E$ and $F$ is an algebraic extension of $K$, it follows that $F$ is an algebraic extension of $E$. Assume that there exists an embedding $\sigma : E \to F$ such that $\sigma(c) = c$ for all $c \in K$. By Theorem (*), there exists an embedding $\tau : F \to F$ that extends $\sigma$. Since $F$ is algebraically closed, $\tau(F)$ is also an algebraically closed field.

Furthermore, because $\sigma(c) = c$ for all $c \in K$ and $\tau$ is an extension of $\sigma$, we have
$$K = \sigma(K) \subset K \subset \sigma(E) \subset \tau(F) \subset F.$$
This implies that $F$ is an algebraic extension of $\tau(F)$. We conclude that $F = \tau(F)$, meaning that $\tau$ is an automorphism. (Finished!!)

Let choose $F = A$ be the field of algebraic numbers, $K=\mathbb{Q}$. Consider the embedding $\sigma: \mathbb{Q}(\sqrt{2}) \to \mathbb{Q}(\sqrt{2}) \subset A$ defined by
$$
a + b\sqrt{2} \mapsto a - b\sqrt{2}.
$$Then, according to the exercise above, $\sigma$ extends to an isomorphism
$$
\bar{\sigma}: A \to A.
$$How should we interpret $\bar{\sigma}$?
10 replies
nguyenalex
Yesterday at 3:58 PM
Royrik123456
Today at 11:38 AM
Generating functions and recursions smelling from 1000 km
Assassino9931   12
N Today at 11:22 AM by sangsidhya
Source: IMC 2022 Day 1 Problem 3
Let $p$ be a prime number. A flea is staying at point $0$ of the real line. At each minute,
the flea has three possibilities: to stay at its position, or to move by $1$ to the left or to the right.
After $p-1$ minutes, it wants to be at $0$ again. Denote by $f(p)$ the number of its strategies to do this
(for example, $f(3) = 3$: it may either stay at $0$ for the entire time, or go to the left and then to the
right, or go to the right and then to the left). Find $f(p)$ modulo $p$.
12 replies
Assassino9931
Aug 5, 2022
sangsidhya
Today at 11:22 AM
ISI 2018 #3
integrated_JRC   34
N Today at 7:08 AM by anudeep
Source: ISI 2018 B.Stat / B.Math Entrance Exam
Let $f:\mathbb{R}\to\mathbb{R}$ be a continuous function such that for all $x\in\mathbb{R}$ and for all $t\geqslant 0$, $$f(x)=f(e^tx)$$Show that $f$ is a constant function.
34 replies
integrated_JRC
May 13, 2018
anudeep
Today at 7:08 AM
Integration Bee Kaizo
Calcul8er   40
N Today at 7:07 AM by Figaro
Hey integration fans. I decided to collate some of my favourite and most evil integrals I've written into one big integration bee problem set. I've been entering integration bees since 2017 and I've been really getting hands on with the writing side of things over the last couple of years. I hope you'll enjoy!
40 replies
Calcul8er
Mar 2, 2025
Figaro
Today at 7:07 AM
k another mathcounts person
Oshawoot   12
N Yesterday at 10:21 PM by elizhang101412
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?
12 replies
Oshawoot
Yesterday at 8:27 PM
elizhang101412
Yesterday at 10:21 PM
another mathcounts person
G H J
G H BBookmark kLocked kLocked NReply
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Oshawoot
83 posts
#1
Y by
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?
Z Y
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Nioronean
82 posts
#2
Y by
Oshawoot wrote:
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?

I think anyone that can get above 40 on chapter has a shot at nationals in any state, you just have to be lucky and not silly
Z Y
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aoh11
157 posts
#3
Y by
yes florida is not competitive so you have a 100% chance of making it
Z Y
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sadas123
911 posts
#4
Y by
Nioronean wrote:
Oshawoot wrote:
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?

I think anyone that can get above 40 on chapter has a shot at nationals in any state, you just have to be lucky and not silly

That's not always the case because this year it is less competitive I am also in Florida but I know many people in my chapter that got 40+ and my chapter is one of the ok chapters in Florida hahahaha :rotfl: here is the top 5 scores 39-39-40-41-41 so I mean it just matters if you practice enough.
This post has been edited 1 time. Last edited by sadas123, Yesterday at 8:35 PM
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aoh11
157 posts
#5
Y by
florida is so good because they got first
Z Y
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maxamc
438 posts
#6
Y by
aoh11 wrote:
florida is so good because they got first

fake news
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Cool12345678
8 posts
#7
Y by
im also in florida!!!
Z Y
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sadas123
911 posts
#8
Y by
maxamc wrote:
aoh11 wrote:
florida is so good because they got first

fake news

Actually Benjamin Jiang got first so technically Florida brought back the win last year.
Z Y
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hashbrown2009
96 posts
#9
Y by
Oshawoot wrote:
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?

depends, 30%-60%
40 on chapter is good, don't silly on state
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hashbrown2009
96 posts
#10
Y by
aoh11 wrote:
florida is so good because they got first

Florida didn't even get top 3 in state rankings
If your talking about individual, your right though
Z Y
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juicetin.kim
2478 posts
#11
Y by
aoh11 wrote:
yes florida is not competitive so you have a 100% chance of making it

:eyes:
Z Y
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alex_xie
92 posts
#12
Y by
Nioronean wrote:
Oshawoot wrote:
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?

I think anyone that can get above 40 on chapter has a shot at nationals in any state, you just have to be lucky and not silly

aint no way not in WA
40=18th in chapter
Z Y
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elizhang101412
1180 posts
#13
Y by
Nioronean wrote:
Oshawoot wrote:
another person asking their chances of nats
im in florida, got 26 sprint and 14 target at chapter, 3rd in countdown
what are my chances of nats?

I think anyone that can get above 40 on chapter has a shot at nationals in any state, you just have to be lucky and not silly

i got 39(sillied a target which would have been 41) and i've never mocked a state score that would qual for any t1 in recent years
Z Y
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