Question: Let $f: R^{+} \rightarrow R: f(x)=\log _{e} x .$ Find $\{x: f(x)=-2\}$
Solution:
Given, $f: R^{+} \rightarrow R: f(x)=\log _{e} x$
$f(x)=-2$
$\log _{e} x=-2$
Taking antilog on both sides
$x=e^{-2}$
Hence, the value of $x$ for which $f(x)=-2$ is $e^{-2}$.
