Example 53

$\;\;\;(11x - 6y)^2$

$=(A - B)^2 \text{, where } A = 11x \text{ and } B = 6y $

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

$=(11x)^2 - 2(11x)(6y) + (6y)^2 $

$=121x^{2} - 132xy +36y^{2}