已知x+y=4,x²+y²=10,求下列各式的值 (1)xy (2)x-y
人气:197 ℃ 时间:2020-03-22 04:03:13
解答
(1)由题:(x+y)²=16
(x+y)²-(x²+y²)=2xy=16-10=6
∴xy=6/2=3
(2)(x-y)²=(x+y)²-4xy=16-12=4
∴x-y=2或-2
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