To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $a$ and $a-1$ is $a\left(a-1\right)$. Multiply $\frac{a-1}{a}$ times $\frac{a-1}{a-1}$. Multiply $\frac{a}{a-1}$ times $\frac{a}{a}$.
Since $\frac{\left(a-1\right)\left(a-1\right)}{a\left(a-1\right)}$ and $\frac{aa}{a\left(a-1\right)}$ 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 $a\left(a-1\right)$ and $a-1$ is $a\left(a-1\right)$. Multiply $\frac{1}{a-1}$ times $\frac{a}{a}$.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $a$ and $a-1$ is $a\left(a-1\right)$. Multiply $\frac{a-1}{a}$ times $\frac{a-1}{a-1}$. Multiply $\frac{a}{a-1}$ times $\frac{a}{a}$.
Since $\frac{\left(a-1\right)\left(a-1\right)}{a\left(a-1\right)}$ and $\frac{aa}{a\left(a-1\right)}$ 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 $a\left(a-1\right)$ and $a-1$ is $a\left(a-1\right)$. Multiply $\frac{1}{a-1}$ times $\frac{a}{a}$.
