Ta có: xy+2x-2y=9
=>x(y+2)-2y-4=9-4
=>x(y+2)-2(y+2)=5
=>(x-2)(y+2)=5
=>\(\left(x-2;y+2\right)\in\left\{\left(1;5\right);\left(5;1\right);\left(-1;-5\right);\left(-5;-1\right)\right\}\)
=>\(\left(x;y\right)\in\left\{\left(3;3\right);\left(7;-1\right);\left(1;-7\right);\left(-3;-3\right)\right\}\)