I think this topic is in the wrong area. Don't you mean to put it in math? I agree with post 2. Quad means 4. A quadratic equation has 2 roots. You can also tell this from the exponent 2.
Well, the quadratic ax^2+bx+c=0 can have maximum 2 roots.
The verdict concerning the number of roots is given by the discriminant of the quadratic.
The discriminant delta is a relation between the coefficients of the quadratic.
delta = b^2-4ac
If delta is positive, b^2-4ac>0, then the quadratic has 2 real different roots.
If delta is zero, b^2-4ac=0, then the quadratic has 2 real equal roots.
If delta is negative, b^2-4ac<0, then the quadratic has no real roots.