(2a²+b²)+2[3a-(a²-b²)] 化简 求值 a是-1 b是2

问题描述:

(2a²+b²)+2[3a-(a²-b²)] 化简 求值 a是-1 b是2

去括号后合并同类项得
3b^2+6a
代入得6

(2a²+b²)+2[3a-(a²-b²)]
=2a²+b²+2[3a-a²+b²]
=2a²+b²+6a-2a²+2b²
=2a²-2a²+2b²+b²+6a
=3b²+6a
=3*2²+6*(-1)
=12-6
=6

(2a²+b²)+2[3a-(a²-b²)] =2a²+b²+2[3a-a²+b²] =2a²+b²+6a-2a²+2b²=3b²+6a=3(2)²+6(-1)=3(4)-6=12-6=6