# How do you factorise a2 - 2ab + b2?

We have to factorise $a^{2}-2ab-b^{2}$

### Solution

$a^{2}-2ab-b^{2}$

=$a^{2}-ab-ab-b^{2}$

=$a(a-b)-b(a-b)$

=$(a-b)(a-b)$

=$(a-b)^{2}$