=>x(y-1)+(y-1)=11
=>(x+1)(y-1)=11
=>\(\left(x+1;y-1\right)\in\left\{\left(1;11\right);\left(11;1\right);\left(-1;-11\right);\left(-11;-1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(0;12\right);\left(10;2\right);\left(-2;-10\right);\left(-12;0\right)\right\}\)