Answer
$b^{2}-4ac$
Work Step by Step
In the quadratic formula,
$x=\displaystyle \frac{-b\pm\sqrt{b^{2}-4ac}}{2a}$
the radicand, $b^{2}-4ac$ could be negative, zero, or positive.
This determines whether and how many real solutions there are.
$b^{2}-4ac\ \ $ is called the discriminant.
