Quadratic Formula Sample Problems

Math Practice Online > free > lessons > Minnesota > 9th grade > Quadratic Formula

If your child needs math practice, click here.

For sample problems, click here.
Here are some tips for Quadratic Formula, which aligns with Minnesota state standards:

The Quadratic Formula

The quadratic formula enables you to solve any equation of the form ax² + bx + c = 0, even if the answers are not integers. If you are unable to factor the trinomial, the quadratic formula is the best way to get the answers.

The quadratic formula is:

The sample problems below will show you how the quadratic formula is used to find the solutions of quadratic equations. The first problem is one that you could also solve using factoring techniques. The second problem uses a trinomial that you would not be able to easily factor.

Problem 1
Solve for x.
x² + x - 2 = 0

Solution
Based on ax² + bx + c, we have:
a = 1, b = 1, c = -2

Plugging into the quadratic formula results in these two answers:

Simplifying...

Final Answer:
x = 1, ^-2

Problem 2
Solve for x.
-x² + 4x + 9 = 0
Solution
Based on ax² + bx + c, we have:
a = -1, b = 4, c = 9

Plugging into the quadratic formula results in these two answers:

Simplifying...

Final Answer:
x = 2 - √13, 2 + √13