Question

y varies directly as the square of x. When x = 4, y = 32. Find x when y = 18.

Answer 1

y = x^2 + C, we need to find C. 32 = 4^2 + C -> 32 = 16 + C -> C = 16. Plug in 18 as y, 18 = x^2 + 16, 2 = x^2. Thus x is the square root of 2. I think this is the solution unless you mean something else.

Answer 2

I disagree. y varies directly with the square of x implies:

y = kx^2

You need to find k. There is no other term.