решите уравнение -х2-6х+7=0

D = b^2 - 4ac

D = 6^2 - 4 * (-1) * 7 = 36 + 28 = 64

x1 = (-b + sqrt(D))/a

x2 = (-b - sqrt(D))/a

x1 = (6 + 8)/(-2) = 14/(-2) = -7

x2 = (6 - 8)/(-2) = -2/(-2) = 1