1)c^2-c-6
2)6a^25a-4
3)20x^2-13xy+2y^2
4)a^3-4a^2+12a-12
1)(a-2)(a+3)
2)a(x-y)+5(x-y)=(a+5)(x-y)
<span>x^2-3x-3y-y^2=(x^2-y^2)-3(x+y)=(x-y)(x+y)-3(x+y)=(x+y)(x-y-3)</span>