If x\ +\ 1over x\ =\ 2√(10 ) , where x > 1, then the value of (x³\ -\ 1over x³) is:

If x\ +\ 1over x\ =\ 2√(10 ) , where x > 1, then the value…

If $x\ +\ {1\over x}\ =\ 2\sqrt{10 }$ , where x > 1, then the value of $\left(x^3\ -\ {1\over x^3}\right)$ is:

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Correct answer: B

Explanation

The correct answer is Option 2 i.e. 234.

$x\ +\ {1\over x}\$ = $\ 2\sqrt{10 }$

$x\ -\ {1\over x}\$ = $\sqrt{a^2-4}$ = $\sqrt{(\ 2\sqrt{10 } )^2-4}$ = 6

$\left(x^3\ -\ {1\over x^3}\right)$ = 6³ + 3 × 6 = 216 + 18 = 234