Using the **quadratic formula** is another method of solving quadratic equations that will not factorise. **You will need to learn this formula, as well as understanding how to use it.**

The quadratic formula for a quadratic equation in the form of is .

Solve using the quadratic formula.

First, identify the value of , and . In this example, , and .

Substitute these values into the quadratic formula:

To calculate the decimal answers, work out each answer in turn on a calculator.

The first solution is (3 sf).

The second solution is (3 sf).

- Question
Solve using the quadratic formula.

Identify , and . , and .

Substitute these values into the quadratic equation .

This gives:

. as two negatives make a positive.

or

(3 sf) or (3 sf)