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设xy=a,1/x^+1/y^2=b,则(x+y)^2=?
人气:237 ℃ 时间:2020-02-04 10:27:00
解答
1/x^2+1/y^2=b
(x^2+y^2)/x^2y^2=b
x^2+y^2=a^2b
(x+y)^2=x^2-2xy+y^2=a^2b-2a
=a(ab-2)
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