Example 95

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

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

$=A^2-B^2$

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

$=81u^{18} - 25v^{18} $