24) A

(x = a) and (x = b)
x – a = 0
x – b = 0

We can write : (x – a) (x – b) = 0
x² – xb – ax + ab = 0

We know (ab) = 3
x² – xb – ax + 3 = 0
x² – x(a + b) + 3 = 0

We know (a + b) = 5
x² – x(5) + 3 = 0
x² – 5x + 3 = 0

Hence A is correct.