# How do you tell whether f(x)=(5/6)^-x is an exponential growth or decay?

${\left(\frac{5}{6}\right)}^{-} x = {\left(\frac{6}{5}\right)}^{x}$
Because $\frac{6}{5} > 1$, if you multiply it by itself $x$ times (as long as $x > 1$) then it will become larger. Therefore, it is exponential growth.