### Factorization of Quadratic Expressions

**Quadratic polynomials** are polynomials of the degree. The standard form of a quadratic polynomial is written as

where and stand for constant numbers. Factoring these polynomials depends on the values of these constants. In this section we’ll learn how to factor quadratic polynomials for different values of and . (When none of the coefficients are zero, these expressions are also called quadratic **trinomials**, since they are polynomials with three terms.)

You’ve already learned how to factor quadratic polynomials where . For example, for the quadratic , the common factor is and this expression is factored as . Now we’ll see how to factor quadratics where is nonzero.

**Factor when a = 1, b is Positive, and c is Positive**

First, let’s consider the case where is positive and is positive. The quadratic trinomials will take the form

You know from multiplying binomials that when you multiply two factors , you get a quadratic polynomial. Let’s look at this process in more detail. First we use distribution:

Then we simplify by combining the like terms in the middle. We get:

So to factor a quadratic, we just need to do this process in reverse.

This means that we need to find two numbers and where

The factors of are always two binomials

such that and .

#### Factoring

1. Factor .

We are looking for an answer that is a product of two binomials in parentheses:

We want two numbers and that multiply to 6 and add up to 5. A good strategy is to list the possible ways we can multiply two numbers to get 6 and then see which of these numbers add up to 5:

So the answer is .

We can check to see if this is correct by multiplying :

The answer checks out.

2. Factor .

We are looking for an answer that is a product of two binomials in parentheses:

The number 12 can be written as the product of the following numbers:

The answer is .

3. Factor .

We are looking for an answer that is a product of two binomials in parentheses:

The number 12 can be written as the product of the following numbers:

The answer is .

### Example

#### Example 1

Factor .

We are looking for an answer that is a product of two binomials in parentheses:

The number 36 can be written as the product of the following numbers:

The answer is .

### Review

Factor the following quadratic polynomials.

### Review (Answers)

To view the Review answers, open this PDF file and look for section 9.8.