Example 85

$\;\;\;(3u + 4v)(3u - 4v)$

$=(A + B)( A - B) \text{ , where } A = 3u \text{ and } B = 4v $

$=A^2-B^2$

$=(3u)^2 - (4v)^2 $

$=9u^{2} - 16v^{2} $