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