# Algebra II : Factoring Polynomials

## Example Questions

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### Example Question #1 : Factoring Polynomials

Find the zeros.

Explanation:

This is a difference of perfect cubes so it factors to . Only the first expression will yield an answer when set equal to 0, which is 1. The second expression will never cross the -axis. Therefore, your answer is only 1.

### Example Question #1 : Factoring Polynomials

Find the zeros.

Explanation:

Factor the equation to . Set  and get one of your 's to be . Then factor the second expression to . Set them equal to zero and you get

### Example Question #3 : Factoring Polynomials

Factor the polynomial:

Explanation:

First, begin by factoring out a common term, in this case :

Then, factor the terms in parentheses by finding two integers that sum to and multiply to :

### Example Question #1 : Factoring Polynomials

Factor the following expression:

Explanation:

Here you have an expression with three variables. To factor, you will need to pull out the greatest common factor that each term has in common.

Only the last two terms have  so it will not be factored out. Each term has at least  and  so both of those can be factored out, outside of the parentheses. You'll fill in each term inside the parentheses with what the greatest common factor needs to be multiplied by to get the original term from the original polynomial:

### Example Question #1 : Trinomials

Which of the following values of  would make the trinomial  prime?

Explanation:

For the trinomial  to be factorable, we would have to be able to find two integers with product 36 and sum ; that is,  would have to be the sum of two integers whose product is 36.

Below are the five factor pairs of 36, with their sum listed next to them.  must be one of those five sums to make the trinomial factorable.

1, 36: 37

2, 18: 20

3, 12: 15

4, 9: 13

6, 6: 12

Of the five choices, only 16 is not listed, so if , then the polynomial is prime.

### Example Question #5 : Factoring Polynomials

Factor the following trinomial: .

None of these answer choices are correct.

Explanation:

To factor trinomials like this one, we need to do a reverse FOIL. In other words, we need to find two binomials that multiply together to yield .

Finding the "first" terms is relatively easy; they need to multiply together to give us , and since  only has two factors, we know the terms must be  and . We now have         , and this is where it gets tricky.

The second terms must multiply together to give us , and they must also multiply with the first terms to give us a total result of . Many terms fit the first criterion. , ,  and  all multiply to yield . But the only way to also get the "" terms to sum to  is to use . It's just like a puzzle!

### Example Question #4641 : Algebra 1

Factor the expression:

Explanation:

To find the greatest common factor, we must break each term into its prime factors:

The terms have , and  in common; thus, the GCF is .

Pull this out of the expression to find the answer:

### Example Question #6 : Factoring Polynomials

Factor the trinomial.

Explanation:

Use the -method to split the middle term into the sum of two terms whose coefficients have sum  and product . These two numbers can be found, using trial and error, to be  and .

and

Now we know that is equal to .

Factor by grouping.

### Example Question #7 : Factoring Polynomials

Factor completely:

The polynomial cannot be factored further.

Explanation:

First, we note that the coefficients have an LCD of 3, so we can factor that out:

We try to factor further by factoring quadratic trinomial . We are looking to factor it into two factors, where the question marks are to be replaced by two integers whose product is  and whose sum is

We need to look at the factor pairs of  in which the negative number has the greater absolute value, and see which one has sum :

None of these pairs have the desired sum, so  is prime.  is the complete factorization.

### Example Question #1 : Factoring Polynomials

Simplify:

Explanation:

When working with a rational expression, you want to first put your monomials in standard format.

Re-order the bottom expression, so it is now reads

Then factor a  out of the expression, giving you .

The new fraction is  .

Divide out the like term, , leaving , or .

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