SOLUTION: 3x (to the 2nd) + 10X - 8

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Question 602561: 3x (to the 2nd) + 10X - 8

Answer by jim_thompson5910(28715) About Me  (Show Source):
You can put this solution on YOUR website!
It looks like you want to factor this.



Looking at the expression 3x%5E2%2B10x-8, we can see that the first coefficient is 3, the second coefficient is 10, and the last term is -8.


Now multiply the first coefficient 3 by the last term -8 to get %283%29%28-8%29=-24.


Now the question is: what two whole numbers multiply to -24 (the previous product) and add to the second coefficient 10?


To find these two numbers, we need to list all of the factors of -24 (the previous product).


Factors of -24:
1,2,3,4,6,8,12,24
-1,-2,-3,-4,-6,-8,-12,-24


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


These factors pair up and multiply to -24.
1*(-24) = -24
2*(-12) = -24
3*(-8) = -24
4*(-6) = -24
(-1)*(24) = -24
(-2)*(12) = -24
(-3)*(8) = -24
(-4)*(6) = -24

Now let's add up each pair of factors to see if one pair adds to the middle coefficient 10:


First NumberSecond NumberSum
1-241+(-24)=-23
2-122+(-12)=-10
3-83+(-8)=-5
4-64+(-6)=-2
-124-1+24=23
-212-2+12=10
-38-3+8=5
-46-4+6=2



From the table, we can see that the two numbers -2 and 12 add to 10 (the middle coefficient).


So the two numbers -2 and 12 both multiply to -24 and add to 10


Now replace the middle term 10x with -2x%2B12x. Remember, -2 and 12 add to 10. So this shows us that -2x%2B12x=10x.


3x%5E2%2Bhighlight%28-2x%2B12x%29-8 Replace the second term 10x with -2x%2B12x.


%283x%5E2-2x%29%2B%2812x-8%29 Group the terms into two pairs.


x%283x-2%29%2B%2812x-8%29 Factor out the GCF x from the first group.


x%283x-2%29%2B4%283x-2%29 Factor out 4 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%2B4%29%283x-2%29 Combine like terms. Or factor out the common term 3x-2


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Answer:


So 3x%5E2%2B10x-8 factors to %28x%2B4%29%283x-2%29.


In other words, 3x%5E2%2B10x-8=%28x%2B4%29%283x-2%29.


Note: you can check the answer by expanding %28x%2B4%29%283x-2%29 to get 3x%5E2%2B10x-8 or by graphing the original expression and the answer (the two graphs should be identical).