The teacher will be very surprised to see your correct solution 😉
a*x^2 + b*x + c = 0
D = b^2 - 4 * a * c =
(-1)^2 - 4 * (1) * (20) = -79
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
____ 1 I*\/ 79 x1 = - - -------- 2 2
____ 1 I*\/ 79 x2 = - + -------- 2 2
x2 = 1/2 + sqrt(79)*i/2
sum
____ ____ 1 I*\/ 79 1 I*\/ 79 - - -------- + - + -------- 2 2 2 2
=
1
product
/ ____\ / ____\ |1 I*\/ 79 | |1 I*\/ 79 | |- - --------|*|- + --------| \2 2 / \2 2 /
=
20
20
x1 = 0.5 - 4.44409720865779*i
x2 = 0.5 + 4.44409720865779*i
x2 = 0.5 + 4.44409720865779*i