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Question
If `"r" - (1)/"r" = 4`; find : `"r"^3 - (1)/"r"^3`
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Solution
`("r" - 1/"r")^3`
=`"r"^3 - (1)/"r"^3 - 3("r" - 1/"r")`
⇒ (4)3 = `"r"^3 - 1/"r"^3 - 3(4)`
⇒ `"r"^3 - (1)/"r"^3`
= 64 + 12
= 76.
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