先化简再求值 m(m-3)-(m+3)(m-3) 其中m=-4

问题描述:

先化简再求值 m(m-3)-(m+3)(m-3) 其中m=-4

m(m-3)-(m+3)(m-3)
=(m-3)(m-m-3)
=-3(m-3)
=-3(-4-3)
=21