1)=4а/(в-а)(в+а) -2(в-а)=
=(4а-2(в+а))/(в-а)(в+а)=
=(4а-2в-2а)/(в-а)(в+а)=
=(2а-2в)/(в-а)(в+а)=
=-2(в-а)/(в-а)(в+а)=-2/(в+а)=
=-2/(-1+2)=-2/1=-2
2)
=х^2(х^2-1)/х^2(х^2+1)=
=(х^2-1)/(х^2+1)=(0.36-1)/(0.36+1)=
=-0.64/1.36=-16/25÷1 9/25=
=-16/25÷34/25=-16/25×25/34=
=-8/17
3)
=7(х-у)(х+у)/5(х^2+ху+у^2) ×
+(х-у)(х^2+ху+у^2)/(х+у)=
=7(х-у)^2/5=7(1.5+3.5)/5=7