If (k + 1/k)^2 = 9, then what is the value of k^3 +1/(k^3) ?

If x + \(\frac{1}{x}\)  = n

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

If $(k + \frac{1}{k})^2 $ = 9

$(k + \frac{1}{k}) $ = 3

Then, $k^3 +\frac{1}{k^3}$ =  3³ - 3 × 3 = 18