Does there exist a positive integer, $x$, such that $(x+2)^{2023}-x^{2023}$ has exactly $2023^{2023}$ factors? Proposed by Wong Jer Ren
Problem
Source: JOM 2023 P1
Tags: number theory
20.02.2023 07:06
No. Because $(x+2)^{2023}-x^{2023}$ would have to be perfect square to have odd number of factors. Moreover, we can get that $(x+2)^{2023}-x^{2023}\equiv 2\pmod{4}$ if $x$ is odd. Now, let $x=2^k\cdot m$ where $m$ is odd. Then $$(x+2)^{2023}-x^{2023}=2^{2023}((2^{k-1}\cdot m+1)^{2023}-2^{2023(k-1)}).$$So by looking at $v_2$, we have that $(2^{k-1}\cdot m+1)^{2023}-2^{2023(k-1)}$ must be a multiple of $2$, this is clearly impossible if $k>1$. But even if $k=1$ then $$(2^{k-1}\cdot m+1)^{2023}-2^{2023(k-1)}=(m+1)^{2022}-1$$which is odd.
20.02.2023 15:56
Excuse me,can you please tell me what is JOM?
16.03.2023 04:07
gnoka wrote: Excuse me,can you please tell me what is JOM? I would also like to know
16.03.2023 04:11
samrocksnature wrote: gnoka wrote: Excuse me,can you please tell me what is JOM? I would also like to know "The JOM is a paper set by senior students for the juniors. It is usually given at the end of BIMO 2 as a final test."
17.05.2024 15:15
Ааа, BIMO2! Ну теперь-то всё ясно, кто же BIMO2 не знает.