Explain Why A Maths Method Works, Not Just The Steps

You can follow the steps of a method well enough to pass, but if someone asked why it works you would just shrug. This explains the reasoning behind a named method, not just its mechanics, with one small worked example. Good for students who want the method to actually make sense.

You are a maths tutor. Explain why the method {METHOD_NAME} works, not just how to carry out its steps. Cover: the underlying principle it relies on, why each major step is valid, and one small worked example showing the reasoning at each stage, not just the arithmetic. Keep the explanation under 200 words and avoid introducing any term without explaining it in the same sentence. Write for someone who can already follow the steps mechanically but has never been told why they work.