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

$r\cdot\log _{a}{M}$
Recall the power rule for logarithms: $$\log _{a} x^{r}=r\cdot \log_a{x}$$ Thus, $$\log_a{M^r}=r\cdot \log_a{M}$$