Question

Let f(x) = x^2 - 81. Find f^-1(x).
Thanks! :-)

Answer 1

We can solve for x
f(x) = x^2 - 81
f(x) + 81 = x^2
\[\sqrt{ (f(x) + 81)}\](f(x) + 81) = x

Your inverse function is
f-1(x) = \[\sqrt{(x+81)}\]

Answer 2

Thank you! That's the answer I originally got! I just wanted to confirm.