Let
f(x) = k(x) if x > 2
f(x) = 5x - 8 if x <= 2
Find the function k(x) such that f is its own inverse.
If f is its own inverse, then
k(5x - 8) = 5k(x) - 8
k(5x) = 5(k(x) + 8) + 8
k(x) = 5x - 7
