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Inequalities from SXTB
sqing   30
N 3 hours ago by sqing
T2811. Let $ a,b,c,d> 0 $ and $ a+b+c+d=1. $ Prove that$\frac{a}{a+1}+\frac{2b}{b+2}+\frac{3c}{c+3}+\frac{6d}{d+6} \leq \frac{12}{13}$
30 replies
sqing
Dec 5, 2024
sqing
3 hours ago
[SHS Sipnayan 2023] Series of Drama F-E
Magdalo   8
N Yesterday at 10:36 PM by trangbui
Find the units digit of
\[\sum_{n=1}^{2025}n^5\]
8 replies
Magdalo
Jun 1, 2025
trangbui
Yesterday at 10:36 PM
max area of triangle of centroids of PBC, PAC,PAB 2017 BMT Individual 16
parmenides51   4
N Yesterday at 9:52 PM by Rice_Farmer
Let $ABC$ be a triangle with $AB = 3$, $BC = 5$, $AC = 7$, and let $ P$ be a point in its interior. If $G_A$, $G_B$, $G_C$ are the centroids of $\vartriangle PBC$, $\vartriangle PAC$, $\vartriangle PAB$, respectively, find the maximum possible area of $\vartriangle G_AG_BG_C$.
4 replies
parmenides51
Jan 3, 2022
Rice_Farmer
Yesterday at 9:52 PM
Daily Problem Writing Practice
KSH31415   16
N Yesterday at 9:09 PM by Vivaandax
I'm trying to get better at writing problems so I decided to challenge myself to write one problem for every day this month (June 2025). I will post them in this thread as well as edit this post with all of them in hide tags. If I can, I'll include a difficulty level in the form of AIME placement. If anybody wants to solve them and give feedback on the problem and/or my difficulty rating, please do!

June 1 (AIME P4) - Solved
June 2 (AIME P5) - Solved
June 3 (AIME P12) - Solved
June 4 (AIME P7)
June 5 (AIME P5)

June 1 (AIME P4)
A bag contains $6$ red balls and $6$ blue balls. A draw consists of randomly selecting $2$ of the remaining balls from bag without replacement, and then setting them aside. A draw is called a match if the two balls have the same color. Compute the expected number of draws until either a match occurs or the bag is empty.
16 replies
KSH31415
Jun 2, 2025
Vivaandax
Yesterday at 9:09 PM
Geometry
Exoticbuttersowo   0
Yesterday at 7:28 PM
In an isosceles triangle ABC with base AC and interior cevian AM, such that MC = 2 MB, and a point L on AM, such that BLC = 90 degrees and MAC = 42 degrees. Determine LBC.
0 replies
Exoticbuttersowo
Yesterday at 7:28 PM
0 replies
(own problem) polynomials
nithish_kumar138   2
N Yesterday at 7:18 PM by Mathelets
When x^4-2x^2-3x^2+7x-2 is divided by x-2 the remainder is 'K'.
By using K find α,β,γ.
Let K= α²+β²+γ²
N=(α+β)²+(β+ γ)²+(γ+α)²
K'= α*β*γ/α+β.
Find K+N+K'....~Nithish
2 replies
nithish_kumar138
Yesterday at 6:31 PM
Mathelets
Yesterday at 7:18 PM
find the value,please…
Cirno-fumofumo   1
N Yesterday at 4:52 PM by vanstraelen
cos(9π/13)*cos(3π/13)+cos(3π/13)*cos(π/13)+cos(9π/13)*cos(π/13)=?
1 reply
Cirno-fumofumo
May 31, 2025
vanstraelen
Yesterday at 4:52 PM
A problem of the number of paths in grid
Nikolai220   2
N Yesterday at 4:45 PM by Zhiyi
How many distinct paths are there from the bottom-left corner to the top-right corner of a 5×5 grid, where each edge can be traverled at most once?(not all edges must be travelled)

(further problem:how many paths are there if the grid is n*n?)
2 replies
Nikolai220
Yesterday at 12:45 PM
Zhiyi
Yesterday at 4:45 PM
Trig Identity
mithu542   6
N Yesterday at 4:30 PM by nithish_kumar138
Prove the following identity:
$$\dfrac{1+\tan \theta}{1-\tan \theta}=\tan \left(\theta+\dfrac{\pi}{4}\right),$$where $\theta$ is in radians.
6 replies
mithu542
Mar 20, 2025
nithish_kumar138
Yesterday at 4:30 PM
Graph of 100 vertices. Each of degree 3. Is that possible?
Clueid   3
N Yesterday at 3:27 PM by KSH31415
Does there exist a graph with 100 vertices with each vertex having a degree of 3? If so, show that it exists. Otherwise, prove it's impossible to exist.
3 replies
Clueid
Yesterday at 3:55 AM
KSH31415
Yesterday at 3:27 PM
a