(4/3a^2b^2-2ab)*1/2ab=2/3ab-1
-2a^2*(-1/2ab+b^2)-5a*(a^2b+ab^2)=a^3b-2a^2b^2-5a^3b-5a^2b^2=-4a^3b-7a^2b^2
(3/2xy+x^2-y^2)(-2xy)-(-xy)^2=-3x^2y^2-2x^3y+2xy^3-x^2y^2=2xy^3-2x^3y-4x^2y^2