已知（2000-a)(1998-a)=1999,计算（2000-a)^2+(1998-a)^2
百度知道里有这题目的答案和过程,但我希望有分析,
人气：121 ℃ 时间：2019-08-19 20:44:40
解答
(x-y)^2=x^2+y^2-2xy
显然要求的是x^2+y^2
2xy=2*1999
(x-y)^2=[(2000-a)-(1999-a)]^2=4
所以答案就是1999*2+4=4002
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