$xy=4(x+y)$ $⇒xy=4x+4y$ $⇒xy-4x-4y=0$ $⇒x(y-4)-4y=0$ $⇒x(y-4)-4y-16+16=0$ $⇒x(y-4)-4(y-4)=16$ $⇒(x-4)(y-4)=16=2.8=1.16=4.4$ $⇒\left[ \begin{array}{l}(x-4; y-4)=(2; 8)⇒(x; y)=(6; 12)\\(x-4; y-4)=(1; 16)⇒(x; y)=(5; 20)\\(x-4; y-4)=(4; 4)⇒(x; y)=(8; 8)\end{array} \right.$ Vậy $(x; y)=(6; 12); (5; 20); (8; 8)$ Trả lời
$xy=4(x+y)$
$⇒xy=4x+4y$
$⇒xy-4x-4y=0$
$⇒x(y-4)-4y=0$
$⇒x(y-4)-4y-16+16=0$
$⇒x(y-4)-4(y-4)=16$
$⇒(x-4)(y-4)=16=2.8=1.16=4.4$
$⇒\left[ \begin{array}{l}(x-4; y-4)=(2; 8)⇒(x; y)=(6; 12)\\(x-4; y-4)=(1; 16)⇒(x; y)=(5; 20)\\(x-4; y-4)=(4; 4)⇒(x; y)=(8; 8)\end{array} \right.$
Vậy $(x; y)=(6; 12); (5; 20); (8; 8)$