已知a(a-1)-(a的平方-b)=4,求二分之a的平方加b的平方-ab的值 快的~急
人气:212 ℃ 时间:2020-03-25 02:54:47
解答
a(a-1)-(a²-b)=4
a²-a-a²+b=4
b-a=4
(a²+b²)/2-ab
=(a²+b²-2ab)/2
=(b-a)²/2
=4²/2
=8(a²+b²)/2-ab=(a²+b²-2ab)/2=(b-a)²/2=4²/2=8 解释下,谢~!就是用了一步完全平法公式啊。先通分,得到(a²+b²-2ab)/2,再对分子用完全平方公式,得到(b-a)²/2,将b-a代入就可以了。很简单的啊。
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