=>(y+1)(3x+1)=7
=>\(\left(3x+1;y+1\right)\in\left\{\left(1;17\right);\left(17;1\right);\left(-1;-17\right);\left(-17;-1\right)\right\}\)
=>\(\left(x,y\right)\in\left\{\left(0;16\right);\left(\dfrac{16}{3};0\right);\left(-\dfrac{2}{3};-18\right);\left(-6;-2\right)\right\}\)