Đáp án:
$(x;y)=(3;4),(-3;-4)$
Giải thích các bước giải:
$\textrm{Ta có:}$
$\dfrac{x}{3}=\dfrac{y}{4}$
$⇔ 4x=3y$
$⇔ x=\dfrac{3y}{4}$
$x^2y^2=144⇔\left[ \begin{array}{l}xy=12\\xy=-12\end{array} \right.(*)$
$\textrm{Thay x vào (*), ta có:}$
$\left[ \begin{array}{l}\dfrac{3y^2}{4}=12\\\dfrac{3y^2}{4}=-12\end{array} \right.$
$⇔ \left[ \begin{array}{l}3y^2=48\\3y^2=-48\end{array} \right.$
$⇔ \left[ \begin{array}{l}y^2=16\\y^2=-16(loại)\end{array} \right.$
$⇔ y^2=16$
$⇔ \left[ \begin{array}{l}y=4\\y=-4\end{array} \right.$
$⇔ \left[ \begin{array}{l}x=3\\x=-3\end{array} \right.$
