## College Algebra (11th Edition)

$x=\ln5$ or $x=\ln3$
Let $u=e^x$ $e^{2x}-8^x+15=0$ $u^2-8u+15=0$ Factor. $(u-5)(u-3)=0$ Equate each factor to 0. $u=5$ or $u=3$ Since $e^x=u$ $e^x=5$ or $e^x=3$ $x=\ln5$ or $x=\ln3$