Unknown process in integration

For the integrand $$\frac{1}{y(1-\frac{y}{L})}$$, cancel common terms in the numerator and denominator:

$$=\int -\frac{L}{y(y-L)}dy$$

This is part of WolframAlpha’s calculations before creating partial fractions. What exactly is this method/theorem? And how does it work?

For the integrand $$\frac{1}{y(1-\frac{y}{L})}$$, cancel common terms in the numerator and denominator:

$$=\int -\frac{L}{y(y-L)}dy$$

This is part of WolframAlpha’s calculations before creating partial fractions. What exactly is this method/theorem? And how does it work?