приведем к оз=(2а-b)*(2a+b)=(4a²-b²)
((3a-b)*(2a+b)-(a-3b)*(2а-b)-8ab+4a²+2b²)/(4a²-b²)=
(6a²+ab-b²-2a²+7ab-3b²-8ab+4a²+2b²)/(4a²-b²)=
(8a²-2b²)/(4a²-b²)=2(4a²-b²)/(4a²-b²)=2
приведем к оз=(2а-b)*(2a+b)=(4a²-b²)
((3a-b)*(2a+b)-(a-3b)*(2а-b)-8ab+4a²+2b²)/(4a²-b²)=
(6a²+ab-b²-2a²+7ab-3b²-8ab+4a²+2b²)/(4a²-b²)=
(8a²-2b²)/(4a²-b²)=2(4a²-b²)/(4a²-b²)=2