(2х+6у)(2х-6у)=4х²-36у²
(6х-2у)(2у+6х)=(6х-2у)(6х+2у)=36х²-4у²
(2ху-6у)(6у+2ху)=(2ху-6у)(2ху+6у=4х²у²-36у²
(6ху-2у)(2у+6ху)=(6ху-2у)(6ху+2у)=36х²у²-4у²
(2х+6у)(2х-6у)=4х²-36у²
(6х-2у)(2у+6х)=(6х-2у)(6х+2у)=36х²-4у²
(2ху-6у)(6у+2ху)=(2ху-6у)(2ху+6у=4х²у²-36у²
(6ху-2у)(2у+6ху)=(6ху-2у)(6ху+2у)=36х²у²-4у²