SOLUTION: How do you factor 2y^2-15y+12?

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Question 351365: How do you factor 2y^2-15y+12?
Found 2 solutions by jim_thompson5910, checkley77:
Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!

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 :
1,2,3,4,6,8,12,24
-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 .
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 :


First NumberSecond NumberSum
1241+24=25
2122+12=14
383+8=11
464+6=10
-1-24-1+(-24)=-25
-2-12-2+(-12)=-14
-3-8-3+(-8)=-11
-4-6-4+(-6)=-10



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.


If you need more help, email me at
jim_thompson5910@hotmail.com

Also, feel free to check out my tutoring website

Jim

Answer by checkley77(12844)   (Show Source): You can put this solution on YOUR website!
2y^2-15y+12
Use the formula below.

y=(15+-sqrt[-15^2-4*2*12])/2*2
y=(14+-sqrt[225-96])/4
y=(15+-sqrt129)/4
y=(15+-11.3578)/4
y=(15+11.3578)/4
y=26.3578/4
y=6.589 ans.
y=(15-11.3578)/4
y=3.64/4
y=.91 ans.

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