Example 47

$\;\;\;(8k - l)^2$

$=(A - B)^2 \text{, where } A = 8k \text{ and } B = l $

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

$=(8k)^2 - 2(8k)(l) + (l)^2 $

$=64k^{2} - 16kl +l^{2} $