Question

[Nguyễn Đình Phương Nhu]

Cho hệ pt :      8x-y=6

                       x^2-y=-6                       
Tks các bạn nhé

Answer 1

[Nguyễn Lê Phước Thịnh]

\(\left\{{}\begin{matrix}8x-y=6\\x^2-y=-6\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}8x-y-x^2+y=6+6\\8x-y=6\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x^2-8x=-12\\y=8x-6\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x^2-8x+12=0\\y=8x-6\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}\left(x-2\right)\left(x-6\right)=0\\y=8x-6\end{matrix}\right.\)

=>\(\left\{{}\begin{matrix}x\in\left\{2;6\right\}\\y=8x-6\end{matrix}\right.\)

Khi x=2 thì \(y=8\cdot2-6=16-6=10\)
Khi x=6 thì \(y=8\cdot6-6=42\)