Х2-8х+15 ----------------- Х2+7х-30
Х^2-3х-5х+15 =-------------------= х^2+10х-3х-30 х(х-3)-5(х-3) =------------------------= х(х+10)-3(х+10) (х-5)(х-3) =--------------= (х+10)(х-3) х-5 =-------- х+10