SOLUTION: I need help expressing the following quadratic expression in factored from by using the quadratic formula : x^2-2ax+a^2-b^2

Question 209704: I need help expressing the following quadratic expression in factored from by using the quadratic formula : x^2-2ax+a^2-b^2
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
You don't need to use the quadratic formula.

Start with the given expression.

We're going to ignore the last term (for now) and focus on factoring the first three terms.

Looking at the expression , we can see that the first coefficient is , the second coefficient is , and the last coefficient is .

Now multiply the first coefficient by the last coefficient to get .

Now the question is: what two whole numbers multiply to (the previous product) and add to the second coefficient ?

To find these two numbers, we need to list all of the factors of (the previous product).

Factors of :
1
-1

Note: list the negative of each factor. This will allow us to find all possible combinations.

These factors pair up and multiply to .
1*1 = 1
(-1)*(-1) = 1

Now let's add up each pair of factors to see if one pair adds to the middle coefficient :

First Number	Second Number	Sum
1	1	1+1=2
-1	-1	-1+(-1)=-2

From the table, we can see that the two numbers and add to (the middle coefficient).

So the two numbers and both multiply to and add to

Now replace the middle term with . Remember, and add to . So this shows us that .

Replace the second term with .

Group the terms into two pairs.

Factor out the GCF from the first group.

Factor out the GCF from the second group.

Combine like terms.

Condense.

So factors to

----------------------------------

So becomes

Notice how we have a difference of squares where in this case and .

So let's use the difference of squares formula to factor the expression:

Start with the difference of squares formula.

Plug in and .

So this shows us that factors to .

In other words .

============================================================

Answer:

So completely factors to

In other words,

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