if ' x cube + 1/x cube = 14 ' find ' x + 1/x '

Asked by adityaprakhar | 23rd Aug, 2010, 04:33: PM

Expert Answer:

x3 + 1/x3 = 14
(x + 1/x)3 =  x3 + 3(x + 1/x) + 1/x3
(x + 1/x)3 =  14 + 3(x + 1/x)
X = x + 1/x, then,
X3 =  14 + 3X
X3  -  3X - 14 = 0
Now by trial an error, we find X ~ 2.8125 = x + 1/x.
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Answered by  | 23rd Aug, 2010, 09:45: PM

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