Question

If $f:R\to R,f\left(x\right)=3x-4$, then $f^{-1}\left(x\right)$ is equal to

• A. $\frac{1}{3}(x-4)$
• B. $\frac{1}{3}(x+4)$
• C. $3x+4$
• D. undefined

Answer 1

Answer: (B)

$\frac{1}{3}(x+4)$

Let $y=f^{-1}\left(x\right)$

$\Rightarrow x=f\left(y\right)=3y-4$

$\Rightarrow y=\frac{x+4}{3}$