(3x+4y)^2-(4y-3x)^2=48xy докозать тождества
(3х+4у)^2-(4у-3х)^2=48ху (3х+4у)^2-(4у-3х)^2=9х^2+24ху+16у^2-(16у^2-24ху+9х^2)=9х^2+24ху+16у^2-16у^2+24ху-9х^2=24ху+24ху=48ху 48ху=48ху