(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
答
2b2+2a2 +2ab
答
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