\(xy+x+y=4\)
\(\Leftrightarrow xy+x+y+1=5\)
\(\Leftrightarrow\left(x+1\right)\left(y+1=5\right)\)
\(Có:5=5.1=\left(-5\right).\left(-1\right)\)
\(\Rightarrow\left(x+1;y+1\right)\in\left\{\left(5;1\right);\left(1;5\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)
\(\Rightarrow\left(x,y\right)\in\left\{\left(4;0\right);\left(0;4\right);\left(-6;-2\right);\left(-2;-6\right)\right\}\)