Discriminant

What is it and how do you find it?

What is it?

It is the number of solutions a quadratic has. The solutions (aka roots or zeros) are where the quadratic intersects the x-axis.

The discriminant is a number calculated by using the formula b^2-4ac.

If its value is positive (greater than zero), the quadratic has 2 solutions.

If its value is zero, the quadratic has 1 solution.

If its value is negative (less than zero), the quadratic has 2 complex (imaginary) solutions.

How do you find it?

Put the quadratic equation in standard for (ax^2+bx+c=0). List your a, b and c. Finally, plug the values into b^2-4ac

Try these...

Find the discriminant and describe the number and type of roots.
1. x^2-9=3x
2. 4x^2+10x+9=0
3. 9x^2+12x+4=0

Your answers...

What does this mean?

If you graphed #1, it would intersect the x-axis 2 times.

If you graphed #2, it would not intersect the x-axis at all.

If you graphed #3, it would sit on the x-axis, intersecting it one time.