SOLUTION: Factor: x^2+6x-16

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Question 125884: Factor:

x^2+6x-16

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

Looking at 1x%5E2%2B6x-16 we can see that the first term is 1x%5E2 and the last term is -16 where the coefficients are 1 and -16 respectively.

Now multiply the first coefficient 1 and the last coefficient -16 to get -16. Now what two numbers multiply to -16 and add to the middle coefficient 6? Let's list all of the factors of -16:



Factors of -16:
1,2,4,8

-1,-2,-4,-8 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to -16
(1)*(-16)
(2)*(-8)
(-1)*(16)
(-2)*(8)

note: remember, the product of a negative and a positive number is a negative 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
1-161+(-16)=-15
2-82+(-8)=-6
-116-1+16=15
-28-2+8=6



From this list we can see that -2 and 8 add up to 6 and multiply to -16


Now looking at the expression 1x%5E2%2B6x-16, replace 6x with -2x%2B8x (notice -2x%2B8x adds up to 6x. So it is equivalent to 6x)

1x%5E2%2Bhighlight%28-2x%2B8x%29%2B-16


Now let's factor 1x%5E2-2x%2B8x-16 by grouping:


%281x%5E2-2x%29%2B%288x-16%29 Group like terms


x%28x-2%29%2B8%28x-2%29 Factor out the GCF of x out of the first group. Factor out the GCF of 8 out of the second group


%28x%2B8%29%28x-2%29 Since we have a common term of x-2, we can combine like terms

So 1x%5E2-2x%2B8x-16 factors to %28x%2B8%29%28x-2%29


So this also means that 1x%5E2%2B6x-16 factors to %28x%2B8%29%28x-2%29 (since 1x%5E2%2B6x-16 is equivalent to 1x%5E2-2x%2B8x-16)



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Answer:
So x%5E2%2B6x-16 factors to %28x%2B8%29%28x-2%29