# Algebra 1 : How to factor a polynomial

## Example Questions

### Example Question #51 : How To Factor A Polynomial

Factor the following:

Explanation:

Using the FOIL rule, only  yields the same polynomial as given in the question.

### Example Question #51 : How To Factor A Polynomial

Factor the following polynomial:

Can't be factored

Explanation:

When asked to factor a difference of squares, the solution will always be the square roots of the coefficients with opposite signs in each pair of parentheses.

### Example Question #361 : Variables

Solve by factoring:

Prime

Explanation:

Here . Multiply  and  and you get  which can be factored as  and  and when one adds  and  you get .  Hence the quadratic equation can be rewritten as

Now you factor by grouping the first two terms and the last two terms giving us

which can be further factored resulting in

By setting each of the two factors to 0 we get

### Example Question #11 : Solving By Factoring

Factor the polynomial.

Explanation:

To factor a polynomial of the form , we want to look at the factors of  and the factors of . We want to find the combination of factors which when multiplied and added together give the value of .

In our case, , and .

The factors for  are .

The factors for  are

Since  is  we will want to use the factors  because .

Therefore when we put these factors into the binomal form we get,

.

Also see that

will foil out into the original polynomial, as , the coefficient for our  term, and , the constant.

### Example Question #51 : How To Factor A Polynomial

What is the simplified reciprocal of the following expression?

Explanation:

There are two steps to this question that can be completed in either order.

1. Simplify the expression

2. Find the reciprocal of the expression

The reciprocal is equivalent to 1 divided by the number (1/x), essentially flipping the position of the numerator and denominator. Simplify first by recognizing you can factor the numerator:

You can simplify the expression by cancelling out on the top and bottom.

This leaves us with .

Now we find the reciprocal by dividing 1 by the number:

In the reverse order it would look like this:

*Always remember what the question is asking.

### Example Question #51 : How To Factor A Polynomial

Factor this polynomial:

.

Explanation:

The key to factoring the polynomial is recognizing a "product of a sum and a difference". The resulting inner terms cancel each other out in the final expanded polynomial.

.

One could use the FOIL and grid methods to factor the polynomial into

.

### Example Question #371 : Variables

Factor the following expression:

not factorable

Explanation:

We are going to use factoring by grouping to factor this expression.

The expression:

has the form:

In factoring by grouping, we want to split that B value into two smaller values a and b so we end up with this expression:

The rules are:

and

For our problem A=6 B=-13 C=6

So we have:

Another way of saying this is that we are looking for factors of 36 that add up to -13

The values that work are:

Plugging those values in:

Now let's group and factor out from both groups:

Finally let's factor  out a (2x-3) from both terms: and we get our answer:

### Example Question #52 : How To Factor A Polynomial

Factor the following:

Explanation:

To factor this you need to see what two numbers multiply together to give you  but add together to give you . There are a number of ways to test and find the answer (such as the cross method) but you will get

because   and

### Example Question #53 : How To Factor A Polynomial

Factor:

Explanation:

First, we see that the second term of this trinomial is negative, while the third term is positive. This should tell us that the binomials we factor out will have negative signs, because adding two negatives equals a negative, while multiplying them equals a positive.

Next we need to determine what are the factors of the third term (in this case, ). We know that & and  &  are the only factors of . So we must figure out which ones add together to equal . As we said before, we know that both will be negative, so we test them out:

This one is correct!

So the factors must be .

To double-check, trying FOILing to see if it's correct.

### Example Question #371 : Variables

Solve for all values of :

Explanation:

First step is to get the equation into a form we can factor by moving the -4 to the left side:

Now to factor this into two binomials we need factors of 8 that add up to 6: 4 and 2.

So we factor the expression to:

Now if either of those binomials equal zero, we have a solution.

The first binomial equals zero when x=-4, and the second binomial equals zero when x=-2.