[ ab(1 - a) - 2a(b - 1/2) ] X [ 2(a^3)b"]
= a [ b(1 - a) - 2(b - 1/2) ] X [ 2(a^3)b"]
= [ b - ab - 2b - 1 ] X [ 2(a^4)b"]
= [ -1 - b - ab ] X 2(a^4)b"
= -2(a^4)b" - 2(a^4)(b^3) - 2(a^5)(b^3)