SOLUTION: Factor the quadratic expression. y^2 - 4y + 4

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Question 383973: Factor the quadratic expression.
y^2 - 4y + 4
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Looking at the expression y%5E2-4y%2B4, we can see that the first coefficient is 1, the second coefficient is -4, and the last term is 4.


Now multiply the first coefficient 1 by the last term 4 to get %281%29%284%29=4.


Now the question is: what two whole numbers multiply to 4 (the previous product) and add to the second coefficient -4?


To find these two numbers, we need to list all of the factors of 4 (the previous product).


Factors of 4:
1,2,4
-1,-2,-4


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


These factors pair up and multiply to 4.
1*4 = 4
2*2 = 4
(-1)*(-4) = 4
(-2)*(-2) = 4

Now let's add up each pair of factors to see if one pair adds to the middle coefficient -4:


First NumberSecond NumberSum
141+4=5
222+2=4
-1-4-1+(-4)=-5
-2-2-2+(-2)=-4



From the table, we can see that the two numbers -2 and -2 add to -4 (the middle coefficient).


So the two numbers -2 and -2 both multiply to 4 and add to -4


Now replace the middle term -4y with -2y-2y. Remember, -2 and -2 add to -4. So this shows us that -2y-2y=-4y.


y%5E2%2Bhighlight%28-2y-2y%29%2B4 Replace the second term -4y with -2y-2y.


%28y%5E2-2y%29%2B%28-2y%2B4%29 Group the terms into two pairs.


y%28y-2%29%2B%28-2y%2B4%29 Factor out the GCF y from the first group.


y%28y-2%29-2%28y-2%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.


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


%28y-2%29%5E2 Condense the terms.


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Answer:


So y%5E2-4y%2B4 factors to %28y-2%29%5E2.


In other words, y%5E2-4y%2B4=%28y-2%29%5E2.


Note: you can check the answer by expanding %28y-2%29%5E2 to get y%5E2-4y%2B4 or by graphing the original expression and the answer (the two graphs should be identical).


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

Also, feel free to check out my tutoring website

Jim