SOLUTION: Can someone please help me with this problem. I tried to do the problem and I just keep getting very confused. We are specifically looking for how to factor polynomials when the

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Can someone please help me with this problem. I tried to do the problem and I just keep getting very confused. We are specifically looking for how to factor polynomials when the      Log On


   



Question 115655: Can someone please help me with this problem. I tried to do the problem and I just keep getting very confused.
We are specifically looking for how to factor polynomials when the leading coefficient is not 1. How can we find the correct way to break up the middle term to make this come out right.
Can you please factor the polynomial
4x^2 + 4x - 99
Please tell us why and how you carry out each step of the process.
PLEASE HELP ME!!!!

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

Looking at 4x%5E2%2B4x-99 we can see that the first term is 4x%5E2 and the last term is -99 where the coefficients are 4 and -99 respectively.

Now multiply the first coefficient 4 and the last coefficient -99 to get -396. Now what two numbers multiply to -396 and add to the middle coefficient 4? Let's list all of the factors of -396:



Factors of -396:
1,2,3,4,6,9,11,12,18,22,33,36,44,66,99,132,198,396

-1,-2,-3,-4,-6,-9,-11,-12,-18,-22,-33,-36,-44,-66,-99,-132,-198,-396 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to -396
(1)*(-396)
(2)*(-198)
(3)*(-132)
(4)*(-99)
(6)*(-66)
(9)*(-44)
(11)*(-36)
(12)*(-33)
(18)*(-22)
(-1)*(396)
(-2)*(198)
(-3)*(132)
(-4)*(99)
(-6)*(66)
(-9)*(44)
(-11)*(36)
(-12)*(33)
(-18)*(22)

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


Now which of these pairs add to 4? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to 4

First NumberSecond NumberSum
1-3961+(-396)=-395
2-1982+(-198)=-196
3-1323+(-132)=-129
4-994+(-99)=-95
6-666+(-66)=-60
9-449+(-44)=-35
11-3611+(-36)=-25
12-3312+(-33)=-21
18-2218+(-22)=-4
-1396-1+396=395
-2198-2+198=196
-3132-3+132=129
-499-4+99=95
-666-6+66=60
-944-9+44=35
-1136-11+36=25
-1233-12+33=21
-1822-18+22=4



From this list we can see that -18 and 22 add up to 4 and multiply to -396


Now looking at the expression 4x%5E2%2B4x-99, replace 4x with -18x%2B22x (notice -18x%2B22x adds up to 4x. So it is equivalent to 4x)

4x%5E2%2Bhighlight%28-18x%2B22x%29%2B-99


Now let's factor 4x%5E2-18x%2B22x-99 by grouping:


%284x%5E2-18x%29%2B%2822x-99%29 Group like terms


2x%282x-9%29%2B11%282x-9%29 Factor out the GCF of 2x out of the first group. Factor out the GCF of 11 out of the second group


%282x%2B11%29%282x-9%29 Since we have a common term of 2x-9, we can combine like terms

So 4x%5E2-18x%2B22x-99 factors to %282x%2B11%29%282x-9%29


So this also means that 4x%5E2%2B4x-99 factors to %282x%2B11%29%282x-9%29 (since 4x%5E2%2B4x-99 is equivalent to 4x%5E2-18x%2B22x-99)

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Answer:

So 4x%5E2%2B4x-99 factors to %282x%2B11%29%282x-9%29