Let fx 87x 4 8 Find f111 where f1 is the inverse function

Let f(x) = 8^7x - 4 + 8. Find f^-1(11), where f^-1 is the inverse function of f.

Solution

f^-1(11)=x

f(x)=11

8^7x-4+8=11

8^7x-4=3

7x-4=log₈3

7x=4+log₈3

x=(1/7)(4+log₈3)

f^-1(11)=x

f^-1(11)=(1/7)(4+log₈3)