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Question
If x−1x=5 then find x3−1x3.
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Solution
Given: x−1x=5
(x−1x)3=x3−1x3−3.x.1x(x−1x) .................. Using (a−b)3=a3−b3−3ab(a−b)
53=x3−1x3−3(5)
x3−1x3=53+3(5)
x3−1x3=140
Given: x−1x=5
(x−1x)3=x3−1x3−3.x.1x(x−1x) .................. Using (a−b)3=a3−b3−3ab(a−b)
53=x3−1x3−3(5)
x3−1x3=53+3(5)
x3−1x3=140
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