ответ: 7+√139
7-√139
x²-14x-90 = 0
a = 1; b = -14; c = -90
D = b² - 4ac
D = 196 - 4(-90) = 196 + 360 = 556
x1,2 = (-b±√D)/2a
x1,2 = (14±√556)/2
x1,2 = (14±√(4•139))/2
x1,2 = (14±2√139)/2
x1,2 = 2•(7±√139)/2
x1,2 = (7±√139)
x1 = 7+√139
x2 = 7-√139
