Hi

i got this question and not sure what its about:

Find the value of x that minimises

y = 8X^2 (400/X)

for positive x.

Give the required x both exactly (i.e. as a surd).

What do i do?

This is what i started doing but no idea what else:

=> y=8x^2+(400/x)

=> 16x-400x^(-2)

==> 16x-400x^(-2) = 0

Thanks