b: x*(y+2)=-8
=>\(x\left(y+2\right)=1\left(-8\right)=\left(-8\right)\cdot1=\left(-1\right)\cdot8=8\left(-1\right)=2\cdot\left(-4\right)=\left(-4\right)\cdot2=\left(-2\right)\cdot4=4\cdot\left(-2\right)\)
=>\(\left(x;y+2\right)\in\left\{\left(1;-8\right);\left(-8;1\right);\left(-1;8\right);\left(8;-1\right);\left(2;-4\right);\left(-4;2\right);\left(-2;4\right);\left(4;-2\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(1;-10\right);\left(-8;-1\right);\left(-1;6\right);\left(8;-3\right);\left(2;-6\right);\left(-4;0\right);\left(-2;2\right);\left(4;-4\right)\right\}\)
c: xy-2x-2y=0
=>\(x\left(y-2\right)-2y+4=4\)
=>\(x\left(y-2\right)-2\left(y-2\right)=4\)
=>\(\left(x-2\right)\left(y-2\right)=4\)
=>\(\left(x-2\right)\left(y-2\right)=1\cdot4=4\cdot1=\left(-1\right)\cdot\left(-4\right)=\left(-4\right)\cdot\left(-1\right)=2\cdot2=\left(-2\right)\cdot\left(-2\right)\)
=>\(\left(x-2;y-2\right)\in\left\{\left(1;4\right);\left(4;1\right);\left(-1;-4\right);\left(-4;-1\right);\left(2;2\right);\left(-2;-2\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(3;6\right);\left(6;3\right);\left(1;-2\right);\left(-2;1\right);\left(4;4\right);\left(0;0\right)\right\}\)
