Interesting problem

by deraxenrovalo, Mar 23, 2025, 4:53 PM

Given $\triangle$$ABC$ with circumcenter $O$$.\;$Let $P$ be an arbitrary point on $(BOC)$ such that $P$ is outside $(ABC)$$.\;$Let $Q$ be an arbitrary point on $(ABC)$$.\;$$AB$ cuts $(ACP)$ again at $E$ and $AC$ cuts $(ABP)$ again at $F$$.\;$The intersection of $BF$ and $CE$ is $R$$.\;$Let $X$ and $Y$ be the intersection of $EF$ with $(PQC)$ and $(PQR)$ respectively such that $X$, $Y$, $P$ are pairwise distinct.
Show that : $(APX)$, $(BPY)$, $(QPE)$ are coaxial circles

hint
This post has been edited 2 times. Last edited by deraxenrovalo, an hour ago
Reason: Error displayed

Vieta Jumping Unsolved(Reposted)

by Eagle116, Mar 23, 2025, 4:53 PM

The question is:
Let $x_1$, $x_2$, $\dots$, $x_n$ be $n$ integers. If $k>n$ is an integer, prove that the only solution to
$$x_1^2 + x_2^2 + \dots + x_n^2 = kx_1x_2\dots x_n $$is is $x_1 = x_2 = \dots = x_n = 0$.

Find all functions

by Jackson0423, Mar 23, 2025, 4:06 PM

Find all functions F:R->R such that
1/(F(F(x))-F(x))=F(x)
I know x+1/x works..

special sets

by ChubbyTomato426, Mar 23, 2025, 3:58 PM

Let $n$ be a positive integer. A subset $\{a, b, c, d\} \subseteq \{1, 2, . . . , 4n\}$ with four distinct elements is special if there exists a rearrangement $(x, y, z, w)$ of $(a, b, c, d)$ such that $xy -zw = 1$. Prove that the set $\{1, 2, . . . , 4n \}$ cannot be partitioned into $n$ special disjoint sets.
This post has been edited 1 time. Last edited by ChubbyTomato426, 2 hours ago

Prove that P1(x), P2(x) ,... Pn(x) = k has no root

by truongphatt2668, Mar 23, 2025, 2:26 AM

Let $n \in \mathbb{N}^*$ and $P_1(x),P_2(x), \ldots P_n(x) \in \mathbb{Z}[x]$ such that $\mathrm{deg} P_i = 2, \forall i = \overline{1,n}$. Prove that exists many $k \in \mathbb{N}$ such that every equation: $P_i(x) = k, \forall i = \overline{1,n}$ has no real roots

sum divides n-th moment

by navi_09220114, Mar 22, 2025, 1:07 PM

Given four distinct positive integers $a<b<c<d$ such that $\gcd(a,b,c,d)=1$, find the maximum possible number of integers $1\le n\le 2025$ such that $$a+b+c+d\mid a^n+b^n+c^n+d^n$$
Proposed by Ivan Chan Kai Chin
This post has been edited 1 time. Last edited by navi_09220114, Yesterday at 1:14 PM

Geo: incircle, escircle, isotomic conjugate

by XAN4, Mar 19, 2025, 1:39 PM

For $\triangle{ABC}$, Its incircle $\odot I$ and $A-$escircle $\odot I_A$ are tangent to $BC$ at $D$ and $E$ respectively. $AI$ intersects line $BC$ at $J$. Line $AD$ intersects $\odot I$ at $F$, and line $AE$ intersects $\odot I_A$ at $G$. Line $FG$ intersects $BC$ at $H$. Prove that $BJ=CH$.

2x+1 is a perfect square but the following x+1 integers are not.

by Sumgato, Mar 17, 2018, 4:30 PM

Find all positive integers $x$ such that $2x+1$ is a perfect square but none of the integers $2x+2, 2x+3, \ldots, 3x+2$ are perfect squares.

Geometry with parallel lines.

by falantrng, Feb 24, 2018, 12:08 PM

Let $ABCD$ be a cyclic quadrilateral an let $P$ be a point on the side $AB.$ The diagonals $AC$ meets the segments $DP$ at $Q.$ The line through $P$ parallel to $CD$ mmets the extension of the side $CB$ beyond $B$ at $K.$ The line through $Q$ parallel to $BD$ meets the extension of the side $CB$ beyond $B$ at $L.$ Prove that the circumcircles of the triangles $BKP$ and $CLQ$ are tangent .
This post has been edited 1 time. Last edited by falantrng, Feb 24, 2018, 12:11 PM

2, 4, 5-Nim

by cjquines0, Jan 21, 2017, 3:47 PM

Two players, \(A\) (first player) and \(B\), take alternate turns in playing a game using 2016 chips as follows: the player whose turn it is, must remove \(s\) chips from the remaining pile of chips, where \(s \in \{ 2,4,5 \}\). No one can skip a turn. The player who at some point is unable to make a move (cannot remove chips from the pile) loses the game. Who among the two players can force a win on this game?
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  • you can just write "Solution

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  • Hello. May I ask a stupid question: how to turn "Hidden Text" into hidden "Solution" tag?

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  • what i got uncontribbed for posting a nice geo problem?

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  • Can I be a contributor?

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