Example 91

$\;\;\;(5u^{9} + v^{11})(5u^{9} - v^{11})$

$=(A + B)( A - B) \text{ , where } A = 5u^{9} \text{ and } B = v^{11} $

$=A^2-B^2$

$=(5u^{9})^2 - (v^{11})^2 $

$=25u^{18} - v^{22} $