x=√4＋√4＋√4+…
x^2= 4+√4＋√4＋…
咁之後應該點做?
x=√4＋√4＋√4+… (15點)
2008-11-15 10:21 pm
回答 (2)
2008-11-15 10:25 pm
✔ 最佳答案
x = √4 ＋ √4 ＋ √4 + … ─── (1)x2 = 4 + √4 ＋ √4 ＋ … ─── (2)(2) - (1):
x2 - x = 4
x2 - x - 4 = 0
x = {[-(-1)] +- √[(-1)2 - 4(1)(-4)]} / 2
x = [1 +- √17] / 2
因x是正數，所以，x = (1 + √17) / 2
2008-11-15 15:04:12 補充：
下面的朋友做錯了。就算數值對，也要捨去負數的答案，因為x是正數的總和。
參考: Myself~~~
2008-11-15 10:31 pm
x=√4＋√4＋√4+…
x^2= 4+√4＋√4＋…
x^2=4+x
x^2-x+4=0
x=1+-√1^2-4(1)(4)/2(1)
x=(1+-√-15)/2
2008-11-15 14:31:45 補充：
= =丫...係減4 = =做錯左- -你睇上面個位人兄先岩....
x^2= 4+√4＋√4＋…
x^2=4+x
x^2-x+4=0
x=1+-√1^2-4(1)(4)/2(1)
x=(1+-√-15)/2
2008-11-15 14:31:45 補充：
= =丫...係減4 = =做錯左- -你睇上面個位人兄先岩....
收錄日期: 2021-04-23 23:04:03
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20081115000051KK00944