a+b=-2,ab=-3,2(ab-3a)-3(2b-ab)=?
问题描述:
a+b=-2,ab=-3,2(ab-3a)-3(2b-ab)=?
答
2(ab-3a)-3(2b-ab)=2ab-6a-6b+3ab=-6a-6b+ab=-6(a+b)+5ab=-6(-2)+5(-3)=-3
答
2ab-6a-6b+3ab
=5ab-6(a+b)
=5*(-3)-6*(-2)
=-15+12
=-3