If x + (2/x) = 4, what is the value of x³ + (8/x³)?

Question: If x + (2/x) = 4, what is the value of x³ + (8/x³)?

Solution:
Here, x + (2/x) = 4

Now,
x³ + (8/x³)
= (x)³ + (2/x)³
= {(x + (2/x)}³ - 3 . x . 2/x {x + (2/x)}
= 4³ - 3 . 2 . 4
= 64 - 24
= 40