x+1/x=1
x^3 + 1/(x^3)=??
F.4 A math
2007-01-12 10:56 pm
回答 (2)
2007-01-12 11:17 pm
(x+1/x)^3=1
x^3+3x+3/x+1/^3=1
^3+1/x^3=-2
x^3+3x+3/x+1/^3=1
^3+1/x^3=-2
2007-01-12 11:00 pm
x+1/x=1
(x+1/x)^3
=x^3+3x^2(1/x)+3x(1/x^2)+1/x^3
=x^3 + 1/(x^3)+3(x+1/x)
So
1=x^3 + 1/(x^3)+3
x^3 + 1/(x^3)=-2
(x+1/x)^3
=x^3+3x^2(1/x)+3x(1/x^2)+1/x^3
=x^3 + 1/(x^3)+3(x+1/x)
So
1=x^3 + 1/(x^3)+3
x^3 + 1/(x^3)=-2
收錄日期: 2021-04-25 16:50:37
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070112000051KK01760