Question

(a-1/2)[(a+1/2b)²-(a-1/2b)²]﹙a²+1/2ab+b²﹚-2b﹙a⁴-1﹚

化简，a=2，b=-1

Answer 1

(a-1/2)[(a+1/2b)²-(a-1/2b)²]﹙a²+1/2ab+b²﹚-2b﹙a⁴-1﹚
=(a-1/2)*2ab﹙a²+1/2ab+b²﹚-2b﹙a⁴-1﹚
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追问

打错了。是
(a-1/2b)[(a+1/2b)²-(a-1/2b)²]﹙a²+1/2ab+b²﹚-2b﹙a⁴-1﹚
写出详细过程

追答

(a-1/2b)[(a+1/2b)²-(a-1/2b)²]﹙a²+1/2ab+b²﹚-2b﹙a⁴-1﹚
=2ab[a^3-(1/4)ab^+ab^-(1/2)b^3]-2b(a^4-1)
=(3/2)a^b^3-ab^4+2b,
a=2，b=-1时原式=-6-2-2=-10.