Hệ phương trình (2x + 4)(6 - y) = (11 - x)(2y + 6) và 3(x + 1)(y + 1) = (3x + 4)(y + 2

* Hướng dẫn giải

Đáp án D

Ta có:

$$\begin{gathered} \left\{\begin{array}{l}\left(2x+4\right)\left(6-y\right)=\left(11-x\right)\left(2y+6\right)\\ 3\left(x+1\right)\left(y+1\right)=\left(3x+4\right)\left(y+2\right)\end{array}\right. \\ \iff \left\{\begin{array}{l}12x-2xy+24-4y=22y+66-2xy-6x\\ 3xy+3x+3y+3=3xy+6x+4y+8\end{array}\right. \\ \iff \left\{\begin{array}{l}18x-26y-42=0\\ -3x-y-5=0\end{array}\right.\iff \left\{\begin{array}{l}9x-13y=21\\ 3x+y=-5\end{array}\right. \end{gathered}$$