SOLUTION: Factor completely x^3 + 6x^2 + 5x I thought i had it and realize that i didnt. Help please..

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Question 117219: Factor completely x^3 + 6x^2 + 5x I thought i had it and realize that i didnt. Help please..
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

x%5E3%2B6x%5E2%2B5x Start with the given expression


x%28x%5E2%2B6x%2B5%29 Factor out the GCF x


Now let's focus on the inner expression x%5E2%2B6x%2B5




Looking at x%5E2%2B6x%2B5 we can see that the first term is x%5E2 and the last term is 5 where the coefficients are 1 and 5 respectively.

Now multiply the first coefficient 1 and the last coefficient 5 to get 5. Now what two numbers multiply to 5 and add to the middle coefficient 6? Let's list all of the factors of 5:



Factors of 5:
1,5

-1,-5 ...List the negative factors as well. This will allow us to find all possible combinations

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

note: remember two negative numbers multiplied together make a positive number


Now which of these pairs add to 6? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 6

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



From this list we can see that 1 and 5 add up to 6 and multiply to 5


Now looking at the expression x%5E2%2B6x%2B5, replace 6x with 1x%2B5x (notice 1x%2B5x adds up to 6x. So it is equivalent to 6x)

x%5E2%2Bhighlight%281x%2B5x%29%2B5


Now let's factor x%5E2%2B1x%2B5x%2B5 by grouping:


%28x%5E2%2B1x%29%2B%285x%2B5%29 Group like terms


x%28x%2B1%29%2B5%28x%2B1%29 Factor out the GCF of x out of the first group. Factor out the GCF of 5 out of the second group


%28x%2B5%29%28x%2B1%29 Since we have a common term of x%2B1, we can combine like terms

So x%5E2%2B1x%2B5x%2B5 factors to %28x%2B5%29%28x%2B1%29


So this also means that x%5E2%2B6x%2B5 factors to %28x%2B5%29%28x%2B1%29 (since x%5E2%2B6x%2B5 is equivalent to x%5E2%2B1x%2B5x%2B5)

x%28x%2B5%29%28x%2B1%29 Now reintroduce the GCF

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Answer:

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