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x-y=2 x²-y²=10 求 x+y
人气:119 ℃ 时间:2020-05-05 23:11:20
解答
∵x-y=2
x²-y²=10
∴x+y=(x+y)(x-y)÷(x-y)
=(x²-y²)÷(x-y)
=10÷2
=5
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