计算题 先化简后求值:m(m-3)-(m+3)(m-3),其中m=-4.

问题描述:

计算题 先化简后求值:m(m-3)-(m+3)(m-3),其中m=-4.

m(m-3)-(m+3)(m-3)
=m²-3m-m²+9
=9-3m
=9+3x4
=21第2步?m(m-3)-(m+3)(m-3)=m²-3m-(m²-9)=m²-3m-m²+9