Quadratic Equations

Factor, complete the square or use the quadratic formula.

Set the equation equal to zero first.
Try to factor. If not, use x = (−b ± √(b² − 4ac)) / 2a.
The discriminant b² − 4ac tells you how many real solutions: positive means two, zero one, negative none.
Sum of the roots is −b/a, and the product is c/a.

Watch out: Forgetting to set the equation to zero before factoring.

Worked example

Solve x² − 5x + 6 = 0.

Answer: x = 2 or x = 3

Try it yourself

Practice questions for this skill are for signed-in students. A free account is all you need.