\(x\left(1-3y\right)+1-3y-1=-4\)
\(\left(1-3y\right)\left(x+1\right)=-3\)
⇒ (x+1) và (1-3y) ϵ {-1;1;-3;3}
\(\Rightarrow\left(x;y\right)\in\left\{\left(-2;-\dfrac{2}{3}\right);\left(0;\dfrac{4}{3}\right);\left(-4;0\right);\left(2;\dfrac{2}{3}\right)\right\}\)