Example 1

$\;\;\;(2u + v)^2$

$=(A + B)^2 \text{, where } A = 2u \text{ and } B = v $

$=A^2 + 2AB + B^2$

$=(2u)^2 + 2(2u)(v) + (v)^2 $

$=4u^{2} + 4uv +v^{2} $