Example 56

$\;\;\;(5x - 7y^{6})^2$

$=(A - B)^2 \text{, where } A = 5x \text{ and } B = 7y^{6} $

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

$=(5x)^2 - 2(5x)(7y^{6}) + (7y^{6})^2 $

$=25x^{2} - 70xy^{6} +49y^{12} $