The teacher will be very surprised to see your correct solution 😉
a*x^2 + b*x + c = 0
D = b^2 - 4 * a * c =
(-14)^2 - 4 * (1) * (15) = 136
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
sum
____ ____ 7 - \/ 34 + 7 + \/ 34
=
14
product
/ ____\ / ____\ \7 - \/ 34 /*\7 + \/ 34 /
=
15
15
____ x1 = 7 - \/ 34
____ x2 = 7 + \/ 34
x2 = sqrt(34) + 7