a = 1 ; b = -8 ; c = 15
D = b^2-4ac = 64 - 4*15 = 4 = 2^2
x1 = (-b+√D)/2a = (8+2)/2 = 5
x2 = (-b-√D)/2a = (8-2)/2 = 2
a = 1 ; b = -8 ; c = 15
D = b^2-4ac = 64 - 4*15 = 4 = 2^2
x1 = (-b+√D)/2a = (8+2)/2 = 5
x2 = (-b-√D)/2a = (8-2)/2 = 2