Example 9

$\;\;\;(k^{9} + l^{7})^2$

$=(A + B)^2 \text{, where } A = k^{9} \text{ and } B = l^{7} $

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

$=(k^{9})^2 + 2(k^{9})(l^{7}) + (l^{7})^2 $

$=k^{18} + 2k^{9}l^{7} +l^{14} $