Re: [中學] 兩題中一中數理資優班考題

[keith291 (keith)]

※ 引述《CBH (吸逼A去)》之銘言：
: https://imgur.com/Ik8fnCQ
: 3Q
: 第2題少寫=0

1.

令 t = (103-x)^1/5  則 (x-21)^1/5 = (82-t^5)^1/5

原式為

   t + (82-t^5)^1/5 = 2

=> 82-t^5 = (2-t)^5

=> t^4 - 4t^3 + 8t^2 - 8t - 5 = 0

=> (t^2-2t-1)(t^2-2t+5) = 0

=> 實根為 t = 1±√2

=> x = 62±29√2

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