To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $3$ and $2$ is $6$. Multiply $\frac{a\left(a+2\right)}{3}$ times $\frac{2}{2}$. Multiply $\frac{a^{2}-a}{2}$ times $\frac{3}{3}$.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $3$ and $2$ is $6$. Multiply $\frac{a\left(a+2\right)}{3}$ times $\frac{2}{2}$. Multiply $\frac{a^{2}-a}{2}$ times $\frac{3}{3}$.
