The teacher will be very surprised to see your correct solution 😉
a*x^2 + b*x + c = 0
D = b^2 - 4 * a * c =
(0)^2 - 4 * (1) * (7) = -28
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
___ x1 = -I*\/ 7
___ x2 = I*\/ 7
x2 = sqrt(7)*i
sum
___ ___ - I*\/ 7 + I*\/ 7
=
0
product
___ ___ -I*\/ 7 *I*\/ 7
=
7
7