de scos radicalul compus

rad(a-radb) = rad(a+c / 2) - rad(a-c /2), unde c=rad(a^2-b)
c=rad(64-60)=rad4=2
Rad(8-2rad15) = rad(8+2 / 2) - rad(8-2 / 2) =
rad 10/2 - rad 6/2 =
rad5 - rad3.