若X^(1/2)+X^(-1/2)=3 求
a) x+x^-1=?
b)x^2+1/x^2=?
X^(1/2)+X^(-1/2)=3
2009-02-21 4:58 am
回答 (1)
2009-02-21 5:24 am
✔ 最佳答案
a)由X^(1/2)+X^(-1/2)=3,兩邊平方
X + 2X^(1/2) * X^(-1/2) + X^-1= 9
X + 2 + X^-1 = 9
X + X^-1 = 7
b)由 a) :
x + x^-1 = 7
兩邊平方
x^2 + 2x*x^-1 + x^-2 = 49
x^2 + 2 + 1/x^2 = 49
x^2 + 1/^2 = 47
2009-02-20 21:26:47 補充：
最尾打少了個x :
x^2 + 1/x^2 = 47
收錄日期: 2021-04-21 22:02:24
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https://hk.answers.yahoo.com/question/index?qid=20090220000051KK01618