(1)

\begin{align*} \log M-\log N & =\log M+\log N^{-1}\\ & =\log\frac{M}{N} \end{align*}

(2)

\begin{align*} \log_{a^{r}}M & =\frac{1}{\log_{M}a^{r}}\\ & =\frac{1}{r\log_{M}a}\\ & =\frac{1}{r}\log_{a}M \end{align*}

(3)

\begin{align*} \log_{a}b & =\frac{1}{\log_{b}a}\\ & =\frac{\log_{c}b}{\log_{c}a}\\ & =\frac{\log_{a}c}{\log_{b}c} \end{align*}