Consider a quadratic equation with integer coefficients.
Is every integer a possible discriminant?

Prove it.

For b^2-4ac to be an even integer, b^2 must be even. Thus b must be even. Therefore, b^2-4ac = (2k)^2-4ac = 4(k^2-ac) for some integer k. Hence, any even integer not divisible by 4 cannot be a discriminant.

Posted by Bractals on 2005-05-25 05:24:26