Question

If $f\left(x\right)=3x-1$ and if $f^{-1}$ is the inverse function of $f$, what is $f^{-1}\left(5\right)$?

• A. $18$
• B. $\frac{4}{3}$
• C. $\frac{5}{3}$
• D. $2$
• E. $0$

Answer 1

Answer: (D)

$2$

$y=3x-1$

$\Rightarrow x=\frac{y+1}{3}$

$f^{-1}\left(x\right)=\frac{x+1}{3}$

$f^{-1}\left(5\right)=\frac{5+1}{3}=2$