2x^3+x^2-2x-1=2*x^2*x+x^2-2x-1=x^2(2x+1)-1(2x+1)=(x^2-1)(2x+1)=(x-1)(x+1)(2x+1) 4ab-b^3-8a^2+2ab^2=(4ab-8a^2)-(b^3-2ab^2)=4a(b-2a)-b^2(b-2a)=(4a-b^2)(b-2a)