(3а+3в)^2 /(а+в)=(3(а+в)(а+в))/(а+в)=3(а+в)

(2с-6d)^2 /с-3d=(2(c-3d)(c-3d))/(c-3d)=2(c-d)

(3х-6у)^2 /(5х-10у)=(3(х-2у)(х-2у)) /(5(х-2у))=3/5 *(х-2у)

(9х^2 - у^2)/(15х-5у)^2=((3х-у)(3х+у))/(5(3х-у)(3х-у))=(3х+у)/(5(3х-у))