已知(x+y)2=25,xy=3,求x2+y2求x2+y2的值答案是?
人气：177 ℃ 时间：2019-08-20 21:06:01
解答
解
(x+y)²=25
∴x²+2xy+y²=25
∵xy=3
∴x²+y²+6=25
∴x²+y²=19
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