If x+1/x=2 √5 where x > 1, then the value of x^3-1/(x^3) is:

If $x+\frac{1}{x}=2 \sqrt{5}$ 

then the value of $x^3-\frac{1}{x^3}$ ?

If $x+\frac{1}{x}=n$ 

then,  $x-\frac{1}{x}$ = \(\sqrt {n^2 - 4}\)

$x-\frac{1}{x}$= \(\sqrt {20 - 4}\) = 4

If x - \(\frac{1}{x}\)  = n

then, $x^3 - \frac{1}{x^3}$ = n³ + 3 × n

then, $x^3 - \frac{1}{x^3}$ = 4³ + 3 × 2 = 76