SOLUTION: What are the factors of k^2-6k+5?

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Question 195817: What are the factors of k^2-6k+5?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Looking at the expression k%5E2-6k%2B5, we can see that the first coefficient is 1, the second coefficient is -6, and the last term is 5.


Now multiply the first coefficient 1 by the last term 5 to get %281%29%285%29=5.


Now the question is: what two whole numbers multiply to 5 (the previous product) and add to the second coefficient -6?


To find these two numbers, we need to list all of the factors of 5 (the previous product).


Factors of 5:
1,5
-1,-5


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


These factors pair up and multiply to 5.
1*5
(-1)*(-5)

Now let's add up each pair of factors to see if one pair adds to the middle coefficient -6:


First NumberSecond NumberSum
151+5=6
-1-5-1+(-5)=-6



From the table, we can see that the two numbers -1 and -5 add to -6 (the middle coefficient).


So the two numbers -1 and -5 both multiply to 5 and add to -6


Now replace the middle term -6k with -k-5k. Remember, -1 and -5 add to -6. So this shows us that -k-5k=-6k.


k%5E2%2Bhighlight%28-k-5k%29%2B5 Replace the second term -6k with -k-5k.


%28k%5E2-k%29%2B%28-5k%2B5%29 Group the terms into two pairs.


k%28k-1%29%2B%28-5k%2B5%29 Factor out the GCF k from the first group.


k%28k-1%29-5%28k-1%29 Factor out 5 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.


%28k-5%29%28k-1%29 Combine like terms. Or factor out the common term k-1

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Answer:


So k%5E2-6k%2B5 factors to %28k-5%29%28k-1%29.


Note: you can check the answer by FOILing %28k-5%29%28k-1%29 to get k%5E2-6k%2B5 or by graphing the original expression and the answer (the two graphs should be identical).