Ответ:
\[\left( 5x^{2} - 6y^{2} \right)\left( 6x^{2} - 5y^{2} \right) =\]
\[= 30x^{4} - 36x^{2}y^{2} - 25x^{2}y^{2} + 30y^{4} =\]
\[= 30x^{4} - 51x^{2}y^{2} + 30y^{4}.\]
\[\left( 5x^{2} - 6y^{2} \right)\left( 6x^{2} - 5y^{2} \right) =\]
\[= 30x^{4} - 36x^{2}y^{2} - 25x^{2}y^{2} + 30y^{4} =\]
\[= 30x^{4} - 51x^{2}y^{2} + 30y^{4}.\]