1.(a-2b)^2(a+b)=(a^2-4ab+4b^2)(a+b)=a^3-4a^2b+4ab^2+a^2b-4ab^2+b^3=a^3-3a^2b+b^3
2.(-3/4x^2y-3/5x^2y^2)(-xy)^2-(-2x^2y^2-3)(-3+2x^2y^2)
=3/4x^3y^2+3/5x^3y^3+(2x^2y^2+3)(2x^2y^2-3)
=3/4x^3y^2+3/5x^3y^3+4x^4y^4-9