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:
==> 16x-400x^(-2) = 0
16x-400x^(-2) = 0 multiplied through by x^2 gives 16x^3 - 400 = 0.
Do you understand that x^(-2) times x^2 = x^0 = 1? You need to revise your basic algebraic skills.