Đáp án:
Giải thích các bước giải:
$xy+12=x+y$
$⇔xy-x-y=-12$
$⇔x.(y-1)-y+1=-12+1$
$⇔x.(y-1)-(y-1)=-11$
$⇔(x-1).(y-1)=-11=11.(-1)=(-1).11=(-11).1=1.(-11)$
$TH1:(x-1).(y-1)=11.(-1)$
$⇒x=12;y=0$
$TH2:(x-1).(y-1)=(-1).11$
$⇒x=0;y=12$
$TH3:(x-1).(y-1)=-11.1$
$⇒x=-10;y=2$
$TH4:(x-1).(y-1)=1.(-11)$
$⇒x=2;y=-10$
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