Question

The graph of a certain quadratic function does not cross the x-axis. Which of the following are possible values for the discriminant?

A. -18
B. -4
C. 25
D. 0

Answer 1

A or B, no root Discriminant <0

Answer 2

a quadratic equation with 1 root is a perfect square (it's actually 2 identical roots), and has discriminant \(b^2-4ac = 0\)
a quadratic equation with 2 real roots (2 crossings of the x-axis) has a discriminant that is positive \(b^2-4ac>0\)
a quadratic equation with 2 imaginary roots (no crossings of the x-axis) has a discriminant that is negative \(b^2-4ac < 0\)