3x^2-8x-15=0

x1=(8+кор.кв.(64+180))/6=(8+кор.кв.(244))/6=(8+2кор.кв.61)/6          =3.93675

x2=(8-кор.кв.(64+180))/6=(8-кор.кв.(244))/6=(8-2кор.кв.61)/6           =-1.27008

(8+2кор.кв.61)/6    (8-2кор.кв.61)/6     ((8+2кор.кв.61)/6)^2 + ((8-2кор.кв.61)/6)^2

_______________ + _______________ = ______________________________________ =

(8-2кор.кв.61)/6     (8+2кор.кв.61)/6     ((8-2кор.кв.61)/6)*((8+2кор.кв.61)/6)

=-3.4