https://faculty.digipen.edu/~ayoung/MAT357/lesson.html?s=sol&n=intro The problem: $\huge e^{-x}-x=0 $ There is not an exact algabraic way we can express $x$. $\huge \begin{align} f(x) &= e^{-x}-x \\ f'(x) &= -e^{-x}-1 \end{align}$