SOLUTION: Factor completely. 14x squared - 20x + 6

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Question 114220: Factor completely.
14x squared - 20x + 6

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

Looking at we can see that the first term is and the last term is where the coefficients are 14 and 6 respectively.

Now multiply the first coefficient 14 and the last coefficient 6 to get 84. Now what two numbers multiply to 84 and add to the middle coefficient -20? Let's list all of the factors of 84:



Factors of 84:
1,2,3,4,6,7,12,14,21,28,42,84

-1,-2,-3,-4,-6,-7,-12,-14,-21,-28,-42,-84 ...List the negative factors as well. This will allow us to find all possible combinations

These factors pair up and multiply to 84
1*84
2*42
3*28
4*21
6*14
7*12
(-1)*(-84)
(-2)*(-42)
(-3)*(-28)
(-4)*(-21)
(-6)*(-14)
(-7)*(-12)

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


Now which of these pairs add to -20? Lets make a table of all of the pairs of factors we multiplied and see which two numbers add to -20

First NumberSecond NumberSum
1841+84=85
2422+42=44
3283+28=31
4214+21=25
6146+14=20
7127+12=19
-1-84-1+(-84)=-85
-2-42-2+(-42)=-44
-3-28-3+(-28)=-31
-4-21-4+(-21)=-25
-6-14-6+(-14)=-20
-7-12-7+(-12)=-19



From this list we can see that -6 and -14 add up to -20 and multiply to 84


Now looking at the expression , replace with (notice adds up to . So it is equivalent to )




Now let's factor by grouping:


Group like terms


Factor out the GCF of out of the first group. Factor out the GCF of out of the second group


Since we have a common term of , we can combine like terms

So factors to


So this also means that factors to (since is equivalent to )

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