a) x^2 - 2x - 8 = 0

x1 = -2, x2 = 4

D = 4 - 4*1*(-8) = 36

sqrt(D) = 6

x1 = (-(-2) - 6) / 2 = -2

x1 = (-(-2) + 6) / 2 = 4

б) 2x^2 > 128

x^2 > 64

|x| > 8

x > 8, x >= 0

-x > 8, x < 0

x є (-inf; -8) U (8; +inf)

в) x^2 + 2x + 2 < 0

D = 4 - 4*1*2 = -4 < 0

Неравенство не решается