(7х+7у)(-6х-4)-(-х+9у)(5х+1)
(7х+7у)(-6х-4)-(-х+9у)(5х+1) -42х²-28х-42ху-28у-(-5х²-х+45ху+9у) -42х²-28х-42ху-28у+5х²+х-45ху-9у -37х²-27х-87ху-37у