Suppose that the height of a golf ball above the ground is represented by the expression , where is the horizontal displacement of the ball. What is the greatest common factor of the terms in this expression? Could you use the greatest common factor to factor the expression? In this Concept, you'll learn how to find monomial factors of polynomials like the one representing the height of the golf ball in this example.
Guidance
We have been multiplying polynomials by using the Distributive Property, where all the terms in one polynomial must be multiplied by all terms in the other polynomial. In this Concept, you will start learning how to do this process using a different method called factoring .
Factoring: Take the factors that are common to all the terms in a polynomial. Then multiply the common factors by a parenthetical expression containing all the terms that are left over when you divide out the common factors.
Let’s look at the areas of the rectangles again: . The total area of the figure on the right can be found in two ways.
Method 1: Find the areas of all the small rectangles and add them.
Blue rectangle
Orange rectangle
Red rectangle
Green rectangle
Purple rectangle
Total area
Method 2: Find the area of the big rectangle all at once.
The answers are the same no matter which method you use:
Finding the Greatest Common Monomial Factor
Once we get a polynomial in factored form, it is easier to solve the polynomial equation. But first, we need to learn how to factor. Factoring can take several steps because we want to factor completely until we cannot factor any more.
When a common factor is factored from a polynomial, you divide each term by the common factor. What is left over remains in parentheses.
Example A
Factor:
Solution:
1. We see that the factor of 5 divides evenly from all terms.
2. We see that the factor of 3 divides evenly from all terms.
Now we will use examples where different powers can be factored and there is more than one common factor.
Example B
Find the greatest common factor.
Solution:
Notice that the factor appears in all terms of but each term has a different power of . The common factor is the lowest power that appears in the expression. In this case the factor is .
Let’s rewrite:
Factor to get .
Example C
Find the greatest common factor.
Solution:
The common factor is .
When we factor , we obtain .
Guided Practice
Find the greatest common factor.
Solution:
First, look at the coefficients to see if they share any common factors. They do: 4.
Next, look for the lowest power of each variable, because that is the most you can factor out. The lowest power of is . The lowest powers of and are to the first power.
This means we can factor out . Now, we have to determine what is left in each term after we factor out :
Practice
Sample explanations for some of the practice exercises below are available by viewing the following video. Note that there is not always a match between the number of the practice exercise in the video and the number of the practice exercise listed in the following exercise set. However, the practice exercise is the same in both. CK12 Basic Algebra: Polynomial Equations in Factored Form (9:29)
Factor the common factor from the following polynomials.
Mixed Review
 Rewrite in standard form: . State the polynomial's degree and leading coefficient.
 Simplify .
 Multiply by .

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