The teacher will be very surprised to see your correct solution 😉
a*x^2 + b*x + c = 0
D = b^2 - 4 * a * c =
(20)^2 - 4 * (4) * (9) = 256
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
x1 = -9/2
x2 = -1/2
x2 = -1/2
sum
-9/2 - 1/2
=
-5
product
-9*(-1) ------- 2*2
=
9/4
9/4