Answer:
x²-10x+19
Explanation:
Let's replace f(x) for y for now.

To find inverse. make your y into x, and your x into y
>Now you solve for y. subtract 5 from both sides
>Square both sides to get rid of root
>drop root and square (x-5)
(x-5)(x-5) = y-6 >FOIL
x²-5x-5x+25 = y-6 > combine like terms
x²-10x+25 = y-6 >add 6 to both sides
x²-10x+19=y > this is your inverse now put the y into inverse form
x²-10x+19