Answer:
9
Explanation:
The inverse of the inverse is the input
f^-1 (f^-1(9)) = 9
As a proof
f(x) = 4x+5
y = 4x+5
Exchange x and y
x = 4y+5
Solve for y
(x+5) = 4y
(x+5)/4 = y
f^-1 (x) = ( x-5)/4
Then find the inverse of this function
y = ( x-5) /4
Exchange x and y
x = (y-5)/4
4x = y-5
4x+5 = y
Which gives us the original function back
f^-1( input) = 4x+5
Using the value given
f^-1 (9) = ( 9-5)/4=4/4 =1
Using the 1 from the previous part as the input
f^-1( 1) = 4*1+5 = 4+5 = 9