SOLUTION: Factor the trinomial z^2-3z+2

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Question 190256: Factor the trinomial
z^2-3z+2

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

Looking at the expression z%5E2-3z%2B2, we can see that the first coefficient is 1, the second coefficient is -3, and the last term is 2.


Now multiply the first coefficient 1 by the last term 2 to get %281%29%282%29=2.


Now the question is: what two whole numbers multiply to 2 (the previous product) and add to the second coefficient -3?


To find these two numbers, we need to list all of the factors of 2 (the previous product).


Factors of 2:
1,2
-1,-2


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


These factors pair up and multiply to 2.
1*2
(-1)*(-2)

Now let's add up each pair of factors to see if one pair adds to the middle coefficient -3:


First NumberSecond NumberSum
121+2=3
-1-2-1+(-2)=-3



From the table, we can see that the two numbers -1 and -2 add to -3 (the middle coefficient).


So the two numbers -1 and -2 both multiply to 2 and add to -3


Now replace the middle term -3z with -z-2z. Remember, -1 and -2 add to -3. So this shows us that -z-2z=-3z.


z%5E2%2Bhighlight%28-z-2z%29%2B2 Replace the second term -3z with -z-2z.


%28z%5E2-z%29%2B%28-2z%2B2%29 Group the terms into two pairs.


z%28z-1%29%2B%28-2z%2B2%29 Factor out the GCF z from the first group.


z%28z-1%29-2%28z-1%29 Factor out 2 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.


%28z-2%29%28z-1%29 Combine like terms. Or factor out the common term z-1

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Answer:


So z%5E2-3z%2B2 factors to %28z-2%29%28z-1%29.


Note: you can check the answer by FOILing %28z-2%29%28z-1%29 to get z%5E2-3z%2B2 or by graphing the original expression and the answer (the two graphs should be identical).