To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $2^{2}$ and $9$ is $36$. Multiply $\frac{\left(3m\right)^{2}}{2^{2}}$ times $\frac{9}{9}$. Multiply $\frac{4n^{2}}{9}$ times $\frac{4}{4}$.
Since $\frac{9\times \left(3m\right)^{2}}{36}$ and $\frac{4\times 4n^{2}}{36}$ have the same denominator, subtract them by subtracting their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $4$ and $9$ is $36$. Multiply $\frac{9m^{2}}{4}$ times $\frac{9}{9}$. Multiply $\frac{4n^{2}}{9}$ times $\frac{4}{4}$.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $2^{2}$ and $9$ is $36$. Multiply $\frac{\left(3m\right)^{2}}{2^{2}}$ times $\frac{9}{9}$. Multiply $\frac{4n^{2}}{9}$ times $\frac{4}{4}$.
Since $\frac{9\times \left(3m\right)^{2}}{36}$ and $\frac{4\times 4n^{2}}{36}$ have the same denominator, subtract them by subtracting their numerators.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $4$ and $9$ is $36$. Multiply $\frac{9m^{2}}{4}$ times $\frac{9}{9}$. Multiply $\frac{4n^{2}}{9}$ times $\frac{4}{4}$.
