Question

Let $f:R\to R$ be a function defined by $f\left(x\right)=2x+3$. Then find $f^{-1}\left(7\right)$.

Answer 1

Given $f:R\to R$ be a function defined by $f\left(x\right)=2x+3$.....(1).

Let $f^{-1}\left(7\right)=y$

or, $f\left(y\right)=7$ [ Using (1)]

or, $2y+3=7$

or, $y=2$.

So $f^{-1}\left(7\right)=2$.