[中學] 指數對數的題目
有雙重根號的題目:
[√(4+√15)]^x + [√(4-√15)]^x = 8
求x
答案是 2 or -2
雙根號可以化簡
√(4+√15) = √(5/2)+√(3/2)
但接下來就不知如何算了
請板友教導
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