Question

Factorise:
Evaluate {(405)² − (395)²}.

Answer 1

We have:
$$\begin{gathered} \left\{{\left(405\right)}^2-{\left(395\right)}^2\right\}=\left(405+395\right)\left(405-395\right) \\ =\left(800\times 10\right) \\ =8000 \end{gathered}$$

∴ $\left\{{\left(405\right)}^2-{\left(395\right)}^2\right\}=8000$