4a^2-4a^2b+3ab^2-3a^2*b+2ab^2-3b^2-4a^3+3b^3-5ab^2
=4a^2+(-4a^2b-3a^2b)+(3ab^2+2ab^2-5ab^2)-3b^2-4a^3+3b^3
=4a^2-7a^2b-3b^2-4a^3