奇怪的題目
(a + b)^3 = a^3 + 3a^2b + 3ab^2 + b^3 = a^3 + b^3 + 3ab(a + b)
=> a^3 + b^3 = (a + b)^3 - 3ab(a + b)
a = x, b = 1/x
ab = 1 => k = 3
那這樣題目給 x = ... 的意義是?
求講解 完全不會寫
奇怪的題目
(a + b)^3 = a^3 + 3a^2b + 3ab^2 + b^3 = a^3 + b^3 + 3ab(a + b)
=> a^3 + b^3 = (a + b)^3 - 3ab(a + b)
a = x, b = 1/x
ab = 1 => k = 3
那這樣題目給 x = ... 的意義是?
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