## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$x=-\ln (2)$
We need to simplify $8-2e^{-x} =4$ $-2e^{-x} =-4$ This yields: $e^{-x}=2$ Take $\ln$ on both sides to obtain: $\ln e^{-x}=\ln 2$ Since, $\ln e^{a}=a$ So, $-x =\ln 2$ Therefore, $x=-\ln (2)$