SOLUTION: Find the constant term to make x^2-4x a perfect square trinomial

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Question 127519: Find the constant term to make x^2-4x a perfect square trinomial

Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
The process for this involves a just a couple of steps as follows:
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First, make sure the multiplier of the x-squared term is 1. If it is different from 1 you have
to factor out that multiplier from both the x-squared term and the term containing x. In this
problem the multiplier of the x-squared term is 1, so we can skip this step.
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Second, go to the term containing just the "x". Divide its multiplier by 2. Then square this
answer.
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Third, add the squared answer to the terms you were given.
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Let's apply these steps to the problem. You were given:
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x%5E2+-+4x
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We can skip the first step as noted above. The second step tells you to take the -4, divide it
by 2 to get -2, and then square the -2 to get +4.
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The third step tells you to add the plus 4 to what you were given. When you do that you have:
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x%5E2+-+4x+%2B+4
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and that is a perfect square trinomial. It factors into:
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%28x+-+2%29%2A%28x+-+2%29
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and this is equal to %28x+-+2%29%5E2
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You can multiply out %28x+-+2%29%2A%28x+-+2%29 and you will find that the product is equal to
x%5E2+-+4x+%2B+4 just as we made it.
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Notice that the constant portion of the factors (the -2 in x - 2) comes from what you
got by dividing the -4 by 2 in step 2 because that's just the way this method works.
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Hope this helps you to understand how to do problems of this type. Just remember the three steps.
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