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Question
If 3x - `4/x` = 4; and x ≠ 0 find : 27x3 - `64/x^3`
Solution
3x - `4/x` = 4;
We need to find 27x3 - `64/x^3`
Let us now consider the expansion of `( 3x - 4/x )^3` :
`( 3x - 4/x )^3 = 27x^3 - 64/x^3 - 3 xx 3x xx 4/x( 3x - 4/x )`
⇒ `(4)^3 = 27x^3 - 64/x^3 - 144 ["Given :" 3x - 4/x = 4]`
⇒ 64 + 144 = 27x3 - `64/x^3`
⇒ 27x3 - `64/x^3` = 208
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