SOLUTION: 4x^3+8x^2-12x

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Question 257119: 4x^3+8x^2-12x
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

4x%5E3%2B8x%5E2-12x Start with the given expression


4x%28x%5E2%2B2x-3%29 Factor out the GCF 4x


Now let's focus on the inner expression x%5E2%2B2x-3


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Looking at x%5E2%2B2x-3 we can see that the first term is x%5E2 and the last term is -3 where the coefficients are 1 and -3 respectively.

Now multiply the first coefficient 1 and the last coefficient -3 to get -3. Now what two numbers multiply to -3 and add to the middle coefficient 2? Let's list all of the factors of -3:



Factors of -3:
1,3

-1,-3 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to -3
(1)*(-3)
(-1)*(3)

note: remember, the product of a negative and a positive number is a negative number


Now which of these pairs add to 2? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 2

First NumberSecond NumberSum
1-31+(-3)=-2
-13-1+3=2



From this list we can see that -1 and 3 add up to 2 and multiply to -3


Now looking at the expression x%5E2%2B2x-3, replace 2x with -x%2B3x (notice -x%2B3x combines back to 2x. So it is equivalent to 2x)

x%5E2%2Bhighlight%28-x%2B3x%29-3


Now let's factor x%5E2-x%2B3x-3 by grouping:


%28x%5E2-x%29%2B%283x-3%29 Group like terms


x%28x-1%29%2B3%28x-1%29 Factor out the GCF of x out of the first group. Factor out the GCF of 3 out of the second group


%28x%2B3%29%28x-1%29 Since we have a common term of x-1, we can combine like terms

So x%5E2-x%2B3x-3 factors to %28x%2B3%29%28x-1%29


So this also means that x%5E2%2B2x-3 factors to %28x%2B3%29%28x-1%29 (since x%5E2%2B2x-3 is equivalent to x%5E2-x%2B3x-3)



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So our expression goes from 4x%28x%5E2%2B2x-3%29 and factors further to 4x%28x%2B3%29%28x-1%29


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Answer:

So 4x%5E3%2B8x%5E2-12x factors to 4x%28x%2B3%29%28x-1%29