(a-3)²+a-3=(a-3)(a-3+1)=(a-3)(a-2)
(x+y)²+x+y=(x+y)(x+y+1)
y=2-5x и y=-12x
2 - 5x= - 12x
-5x+12x= - 2
7x= - 2 /:7
x= - 2/7