Let's find the GCF of the coefficients, first.  Our coefficients are 3, 9, and -15.  The GCF is 3.  3 is the biggest number that can divide EACH of the numbers without leaving a remainder.

So, 3 is the first part of our GCF.

Next, look at the variables.  THERE IS NO COMMON VARIABLE!  The first term has an "r" variable, but the second term only has a "q" variable.  They do not have anything in common, so we cannon factor out any variables.

So, the only factor all of the terms have in common is "3," and when you divide each of the terms by 3, we get:

At first, it looks like none of the the terms have any factors in common.  But here's how we factor by "grouping":  we separate the four terms into two groups, with two terms in each group.  Then, we find the GCF of each separate group.

First group: 6a + 3

Second group: 8ab + 4b

Start with the first group.  The GCF is "3," since that's the biggest number that can divide each term without leaving a remainder.  So, group 1 is:

Second group.  The GCF is 4b.  Check it, if you're not sure.  That means that when group 2 is factored, we get:

So, since both group 1 and group 2 were being ADDED to each other in our original expression, we can simply add the two factored groups to each other:

The expression is still the same, we've just rewritten it in factored form.  If you multiply through the parentheses, you'll see that we still have the same original expression:

But now, notice that the two factored terms have something in common!  They each have the factor

So, we can divide (2a+1) from both terms, leaving us with:

Group the first two terms together:

Find the GCF:

Group the second two terms together:

Find the GCF:

The two factored terms both have as their GCF.

So, factoring out from each term gives us:

The polynomial factors into (x + 3) (3x - 2).

3x² + 7x – 6 = (a + b)(c + d)

There must be a 3x term to get a 3x² term.

3x² + 7x – 6 = (3x + b)(x + d)

The other two numbers must multiply to –6 and add to +7 when one is multiplied by 3.

b * d = –6 and 3d + b = 7

b = –2 and d = 3

3x² + 7x – 6 = (3x – 2)(x + 3)

(x + 3) is the correct answer.

The product of the last two numbers should be 6, while the sum of the products of the inner and outer numbers should be 5x. Factors of six include 1 and 6, and 2 and 3. In this case, our sum is five so the correct choices are 2 and 3. Then, our factored expression is (x + 2)(x + 3). You can check your answer by using FOIL.

y = x² + 5x + 6

2 * 3 = 6 and 2 + 3 = 5

(x + 2)(x + 3) = x² + 5x + 6

Because both terms are perfect squares, this is a difference of squares:

The difference of squares formula is .

Here, a = x and b = 5.  Therefore the answer is .

You can double check the answer using the FOIL method:

The solutions indicate that the answer is:

and we need to insert the correct addition or subtraction signs. Because the last term in the problem is positive (+4), both signs have to be plus signs or both signs have to be minus signs. Because the second term (-5x) is negative, we can conclude that both have to be minus signs leaving us with:

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

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.

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