(2012•贵阳)先化简,再求值:2b2+(a+b)(a-b)-(a-b)2,其中a=-3,b= 1(2012•贵阳)先化简,再求值:2b2+(a+b)(a-b)-(a-b)2,其中a=-3,b=1 2

问题描述:

(2012•贵阳)先化简,再求值:2b2+(a+b)(a-b)-(a-b)2,其中a=-3,b= 1
(2012•贵阳)先化简,再求值:2b2+(a+b)(a-b)-(a-b)2,其中a=-3,b=
1
2

2b2+2a2 +2ab

2b2+(a+b)(a-b)-(a-b)2,
= 2b2+a²-b²-a²-b²+2ab
= 2b²-2b²+2ab
= 2ab
其中a=-3,b= 1
= -6