Question

What is the formula of $a^2-b^2$?

Answer 1

Determine the formula for $a^2-b^2$.

$\begin{array}{rcl}{a}^2-b^2& =& a^2-ab+ba-b^2\\ & =& a\left(a-b\right)+b\left(a-b\right)\\ & =& \left(a-b\right)\left(a+b\right)\end{array}$

Hence, the formula is $a^2-b^2=\left(a+b\right)\left(a-b\right)$.