Find the Inverse function of f:

f(x)=8+[square root of(8+x)]

f^(-1)(x)=_______, x>8

f = 8+√(8+x)

to find f^-1, swap variables and solve for f:
x = 8+√(8+f)
x-8 = √(8+f)
x^2-16x+64 = 8+f
f = x^2-16x+56