Question

what is the root equation formula?

Answer 1

In the quadratic formula, the expression underneath the square root sign is called the discriminant of the quadratic equation, and is often represented using an upper case "D "

Answer 2

for equation 

ax² + bx +c = 0

$x=\frac{-b+\sqrt{b^2-4ac}}{2a}$   and    $x=\frac{-b-\sqrt{b^2-4ac}}{2a}$