In algebra, letters are used when numbers are not known. Algebraic terms, such as \(2s\) or \(8y\), leave the multiplication signs out. So rather than \(2 \times s\), write \(2s\), and rather than \(8 ...

A mathematical proof is a sequence of statements that follow on logically from each other that shows that something is always true. Using letters to stand for numbers means that we can make statements ...