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) * (15) = -60
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
____ x1 = -I*\/ 15
____ x2 = I*\/ 15
x2 = sqrt(15)*i
sum
____ ____ - I*\/ 15 + I*\/ 15
=
0
product
____ ____ -I*\/ 15 *I*\/ 15
=
15
15