F.4 QUADRATIC EQUATION

Let the 2 roots be h and k.
Since sum of roots = - b/a = h + k
If - b/a = 0, that means h + k = 0, or h = - k.
So if h is positive, k will be negative, if h is negative, k will be positive, therefore, the 2 roots must be opposite sign.
Since product of roots = c/a = hk.
If c/a = 1, that means hk = 1, or h = 1/k or k = 1/h. So the 2 roots are reciprocals of another.