Đáp án:
Giải thích các bước giải:
$\eqalign{ & xy + 2x - y = 5 \cr & \Leftrightarrow x(y + 2) - (y + 2) = 5 - 2 \cr & \Leftrightarrow (x - 1)(y + 2) = 3 \cr & Vi\,x,y\,thuoc\,Z\,nen\,x - 1\,\,va\,\,y + 2\,deu\,la\,so\,nguyen\, \cr & \Rightarrow x - 1\,va\,y + 2\,la\,uoc\,nguyen\,cua\,3 \cr & \Rightarrow \left[ \matrix x - 1 = 3 \Rightarrow y + 2 = 1 \hfill \cr x - 1 = - 3 \Rightarrow y + 2 = - 1 \hfill \cr x - 1 = 1 \Rightarrow y + 2 = 3 \hfill \cr x - 1 = - 1 \Rightarrow y + 2 = - 3 \hfill \cr \endmatrix \right. \Rightarrow \left[ \matrix x = 4,\,y = - 1 \hfill \cr x = - 2,\,y = - 3 \hfill \cr x = 2,\,y = 1 \hfill \cr x = 0,\,y = - 5 \hfill \cr \endmatrix \right. \cr & Thu\,lai\,ta\,c\'o \,tat\,ca\,cac\,gia\,tri\,tim\,duoc\,deu\,thoa\,man \cr & \cr} $
