SOLUTION: 2x^2+27x+56=0 please help factor

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Question 211834: 2x^2+27x+56=0 please help factor
Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
Solved by pluggable solver: Factoring using the AC method (Factor by Grouping)


Looking at the expression , we can see that the first coefficient is , the second coefficient is , and the last term is .



Now multiply the first coefficient by the last term to get .



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



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



Factors of :

1,2,4,7,8,14,16,28,56,112

-1,-2,-4,-7,-8,-14,-16,-28,-56,-112



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



These factors pair up and multiply to .

1*112 = 112
2*56 = 112
4*28 = 112
7*16 = 112
8*14 = 112
(-1)*(-112) = 112
(-2)*(-56) = 112
(-4)*(-28) = 112
(-7)*(-16) = 112
(-8)*(-14) = 112


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



First NumberSecond NumberSum
11121+112=113
2562+56=58
4284+28=32
7167+16=23
8148+14=22
-1-112-1+(-112)=-113
-2-56-2+(-56)=-58
-4-28-4+(-28)=-32
-7-16-7+(-16)=-23
-8-14-8+(-14)=-22




From the table, we can see that there are no pairs of numbers which add to . So cannot be factored.



===============================================================





Answer:



So doesn't factor at all (over the rational numbers).



So is prime.





So make sure that you have the correct problem.

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