To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $m-3$ and $m+3$ is $\left(m-3\right)\left(m+3\right)$. Multiply $\frac{m+3}{m-3}$ times $\frac{m+3}{m+3}$. Multiply $\frac{m-3}{m+3}$ times $\frac{m-3}{m-3}$.
Since $\frac{\left(m+3\right)\left(m+3\right)}{\left(m-3\right)\left(m+3\right)}$ and $\frac{\left(m-3\right)\left(m-3\right)}{\left(m-3\right)\left(m+3\right)}$ have the same denominator, add them by adding their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $m-3$ and $m+3$ is $\left(m-3\right)\left(m+3\right)$. Multiply $\frac{m+3}{m-3}$ times $\frac{m+3}{m+3}$. Multiply $\frac{m-3}{m+3}$ times $\frac{m-3}{m-3}$.
Since $\frac{\left(m+3\right)\left(m+3\right)}{\left(m-3\right)\left(m+3\right)}$ and $\frac{\left(m-3\right)\left(m-3\right)}{\left(m-3\right)\left(m+3\right)}$ have the same denominator, add them by adding their numerators.
