Question

[Lương Bảo Châu]

 Mọi ng giúp mk bài này với ạ ai làm mk tick cho

Answer 1

[Nguyễn Việt Lâm]

\(\Leftrightarrow\left(x^2+xy\right)-\left(x+y\right)-\left(2xy^2-2y^2\right)=1\)

\(\Leftrightarrow x\left(x+y\right)-\left(x+y\right)-2y^2\left(x-1\right)=1\)

\(\Leftrightarrow\left(x-1\right)\left(x+y\right)-2y^2\left(x-1\right)=1\)

\(\Leftrightarrow\left(x-1\right)\left(x+y-2y^2\right)=1=1.1=\left(-1\right).\left(-1\right)\)

Th1: \(\left\{{}\begin{matrix}x-1=1\\x+y-2y^2=1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2\\2+y-2y^2=1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\2y^2-y-1=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2\\\left[{}\begin{matrix}y=1\\y=-\dfrac{1}{2}\left(loại\right)\end{matrix}\right.\end{matrix}\right.\)

Th2: \(\left\{{}\begin{matrix}x-1=-1\\x+y-2y^2=-1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=0\\0+y-2y^2=-1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=0\\2y^2-y-1=0\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=0\\\left[{}\begin{matrix}y=1\\y=-\dfrac{1}{2}\left(loại\right)\end{matrix}\right.\end{matrix}\right.\)

Vậy pt có 2 cặp nghiệm nguyên \(\left(x;y\right)=\left(2;1\right);\left(0;1\right)\)