去括号 -5(3a-2)-3(3a-7)

问题描述:

去括号 -5(3a-2)-3(3a-7)

-5a+2(3a-2)-3(3a-7)
=-5a+(6a-4)-(9a-21)
=-5a+6a-4-9a+21
=(-5+6-9)a-4+21
=-8a+17