Find its inverse

Question

Given the function f(x)=9x+7, find its inverse.

A. f^-1 (x)= (x-9)/7

 

B. f-1(x)=x/9 -7

 

C. f-1(x)=(x-9)-7

 

D. f-1(x)=x/7 -9

 

I keep getting an answer that isn't a choice

Answer 1

To find the inverse replace f(x) with x, and replace x with f^-1(x). Then solve for f^-1(x).

 

f(x) = 9x +7 

x = 9f^-1(x) + 7

x - 7 = 9f^-1(x)

(x - 7/9 = f^-1(x)

 

Me too!