SOLUTION: Factor completely as possible. 9x^2-39x-30 Factor by grouping 10x^2-4xy-15xy+6y^2

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Question 164344: Factor completely as possible.
9x^2-39x-30
Factor by grouping
10x^2-4xy-15xy+6y^2
Found 2 solutions by jim_thompson5910, Earlsdon:
Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
I'll do the first one to get you started

# 1

Start with the given expression


Factor out the GCF


Now let's focus on the inner expression


------------------------------------------------------------




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 :
1,2,3,5,6,10,15,30
-1,-2,-3,-5,-6,-10,-15,-30


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


These factors pair up and multiply to .
1*(-30)
2*(-15)
3*(-10)
5*(-6)
(-1)*(30)
(-2)*(15)
(-3)*(10)
(-5)*(6)

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


First NumberSecond NumberSum
1-301+(-30)=-29
2-152+(-15)=-13
3-103+(-10)=-7
5-65+(-6)=-1
-130-1+30=29
-215-2+15=13
-310-3+10=7
-56-5+6=1



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


So the two numbers and both multiply to and add to


Now replace the middle term with . Remember, and add to . So this shows us that .


Replace the second term with .


Group the terms into two pairs.


Factor out the GCF from the first group.


Factor out 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.


Combine like terms. Or factor out the common term


----------------------------------------------------------------


So our expression goes from and factors further to


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


Answer:

So completely factors to

Answer by Earlsdon(6294)   (Show Source): You can put this solution on YOUR website!
Factor:
First, notice that 3 is a common factor of each of the three terms, so you can factor this.
Now factor the trinomial in parentheses.

Factor by grouping:
Group the terms as shown below:
Notice the change of sign on the last term! Now look for common factors in the terms of each group.
Now you can factor the common factors of (5x-2y)
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