-a-3+(a+3)(a-2)
=-a-3+a^2+a-6
=a^2-9
=(a+3)(a-3)
4p(1-p)^3+2(p-1)^2
=(1-p)^2 * [4p(1-p)+2]
=(p-1)^2 * 2(p-2p^2+1)
= -2(p-1)^2 ( 2p^2 - p - 1)谢啦，太详细了！