SOLUTION: 5. How do I complete this using factoring? Thank you. x^2 + 6x + 5.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: 5. How do I complete this using factoring? Thank you. x^2 + 6x + 5.      Log On


   



Question 156339: 5. How do I complete this using factoring? Thank you.

x^2 + 6x + 5.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Looking at the expression x%5E2%2B6x%2B5, we can see that the first coefficient is 1, the second coefficient is 6, and the last term is 5.


Now multiply the first coefficient 1 by the last term 5 to get %281%29%285%29=5.


Now the question is: what two whole numbers multiply to 5 (the previous product) and add to the second coefficient 6?


To find these two numbers, we need to list all of the factors of 5 (the previous product).


Factors of 5:
1,5
-1,-5


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


These factors pair up and multiply to 5.
1*5
(-1)*(-5)

Now let's add up each pair of factors to see if one pair adds to the middle coefficient 6:


First NumberSecond NumberSum
151+5=6
-1-5-1+(-5)=-6



From the table, we can see that the two numbers 1 and 5 add to 6 (the middle coefficient).


So the two numbers 1 and 5 both multiply to 5 and add to 6


Now replace the middle term 6x with x%2B5x. Remember, 1 and 5 add to 6. So this shows us that x%2B5x=6x.


x%5E2%2Bhighlight%28x%2B5x%29%2B5 Replace the second term 6x with x%2B5x.


%28x%5E2%2Bx%29%2B%285x%2B5%29 Group the terms into two pairs.


x%28x%2B1%29%2B%285x%2B5%29 Factor out the GCF x from the first group.


x%28x%2B1%29%2B5%28x%2B1%29 Factor out 5 from the second group. The goal of this step is to make the terms in the second parenthesis equal to the terms in the first parenthesis.


%28x%2B5%29%28x%2B1%29 Combine like terms. Or factor out the common term x%2B1

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Answer:


So x%5E2%2B6x%2B5 factors to %28x%2B5%29%28x%2B1%29.


Note: you can check the answer by FOILing %28x%2B5%29%28x%2B1%29 to get x%5E2%2B6x%2B5 or by graphing the original expression and the answer (the two graphs should be identical).