Question

Find the inverse of function f. f(x)=9x+7
A. F-1(x)= -9x-7
B.F-1(x)= 1/9x-7/9
C.F-1(x)= 7x+9
D.F-1(x)= 7/9x-1/9

Answer 1

Answer:

B

Step-by-step explanation:

let y = f(x) and rearrange making x the subject, that is

y = 9x + 7 ( subtract 7 from both sides )

y - 7 = 9x ( divide all terms by 9 )

$\frac{1}{9}$ y - $\frac{7}{9}$ = x

Change y back into terms of x with x = $f^{-1}$(x) , thus

$f^{-1}$ (x) = $\frac{1}{9}$ x - $\frac{7}{9}$ → B