To find an inverse function first replace f(x) with y
f(x) = 8*sqrt(x)
y = 8*sqrt(x)
Then, simply switch the places of the x and y.
x = 8sqrt(y)
Now solve for the new y by squaring both sides (to get rid of the root)
x^2 = 64y
divide to get
y = x^2/64. This is the inverse function or option C.