Question

[khgdg]

tim x,y biet:36-y mu 2=8(x-2021) mu 2

Answer 1

[Nguyễn Hoàng Minh]

Bs: \(x,y\in \mathbb{Z}\)

Ta có \(36-y^2=8\left(x-2021\right)^2\ge0\Leftrightarrow y^2\le36\)

Mà \(8\left(x-2021\right)^2\) và 36 chẵn nên y chẵn

Do đó \(y^2\in\left\{4;16;36\right\}\)

Với \(y^2=4\Leftrightarrow8\left(x-2021\right)^2=32\Leftrightarrow\left(x-2021\right)^2=4\Leftrightarrow\left[{}\begin{matrix}x=2025\\x=2017\end{matrix}\right.\)

Với \(y^2=16\Leftrightarrow8\left(x-2021\right)^2=20\Leftrightarrow\left(x-2021\right)^2=\dfrac{5}{2}\left(loại\right)\)

Với \(y^2=36\Leftrightarrow8\left(x-2021\right)^2=0\Leftrightarrow x=2021\)

Vậy \(\left(x;y\right)=\left(2025;2\right);\left(2025;-2\right);\left(2017;2\right);\left(2017;-2\right);\left(2021;6\right);\left(2021;-6\right)\)