Yet another unsolved homework problem, this one involving simple harmonic motion:

"The speed of a point moving along the x-axis is given by

v^2 = 108 + 72x - 36x^2

Find the mean position, the amplitude and the frequency of the motion."

What do they mean find the mean position? Shouldn't it be at the centre? I know that I can use the formula

x = Acos(ωt + α)

to find amplitude (A), and

f = 1/TwhereT = 2π/ω

to find frequency (f)

But I can't even seem to get started. Thanks for any help