The teacher will be very surprised to see your correct solution 😉
a*x^2 + b*x + c = 0
D = b^2 - 4 * a * c =
(-32)^2 - 4 * (15) * (21) = -236
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
sum
____ ____ 16 I*\/ 59 16 I*\/ 59 -- - -------- + -- + -------- 15 15 15 15
=
32 -- 15
product
/ ____\ / ____\ |16 I*\/ 59 | |16 I*\/ 59 | |-- - --------|*|-- + --------| \15 15 / \15 15 /
=
7/5
7/5
____ 16 I*\/ 59 x1 = -- - -------- 15 15
____ 16 I*\/ 59 x2 = -- + -------- 15 15
x2 = 16/15 + sqrt(59)*i/15
x1 = 1.06666666666667 + 0.51207638319124*i
x2 = 1.06666666666667 - 0.51207638319124*i
x2 = 1.06666666666667 - 0.51207638319124*i