※ 引述《ncku0610 (小丸子)》之銘言：
: XY
: ------=3.02
: X+Y
: 5Y 5X
: -------－------= -3.51
: X+Y X+Y
: X=20.3
: Y=3.55
xy/(x+y) = a ---(1)
5y/(x+y) - 5x/(x+y) = b ---(2)
--------------------------
(1) => xy/a=x+y 代入(2)
5ay/(xy) - 5ax/(xy) = b
=> 1/x-1/y = b/(5a) => 1/x = 1/y+ b/(5a) 帶入(1)
因為(1) = 1/(1/y+1/x) = a
所以帶入後 1/(2/y + b/(5a)) = a
分子分母搬一搬就可以了
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