A **quadratic equation** contains only terms up to and including . There are many ways to solve quadratics. All quadratic equations can be written in the form where , and are numbers ( cannot be equal to 0, but and can be).

Here are some examples of quadratic equations.

- . This will expand to and
- . This will expand to and
- . This will rearrange to and
- . This will rearrange to . and (in this example , but has been rearranged to the other side of the equation)
- is an example of a quadratic equation that can be solved simply.

If the product of two numbers is zero then one or both of the numbers must also be equal to zero. Therefore if , then and/or .

If , then or , or both. Factorising quadratics will also be used to solve the equation.

Expanding the brackets gives , which simplifies to . Factorising is the reverse process of expanding brackets, so factorising gives .

Solve .

The product of and is 0, so or , or both.

or .

- Question
Solve .

The product of and is 0, so or .

or

- Question
Solve .

Begin by factorising the quadratic.

The quadratic will be in the form .

Find two numbers with a product of 12 and a sum of 7.

, and , so and are equal to 3 and 4. This gives:

The product of and is 0, so or , or both.

or