Example 106

$\;\;\;(x^{5}y^{5} + 9)(x^{5}y^{5} - 9)$

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

$=A^2-B^2$

$=(x^{5}y^{5})^2 - (9)^2 $

$=x^{10}y^{10} - 81 $