设A=2a2-b,B=-a2+b,求:(1)A-2B;(2)当a=-2,b=-3时,计算A-2B的值

2024-12-28 11:04:04
推荐回答(1个)
回答1:

(1)A-2B=(2a2-b)-2(-a2+b)
=2a2-b+2a2-2b
=4a2-3b;

(2)A-2B=4a2-3b
=4×(-2)2-3×(-3)
=25.