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Quadratic Formula

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Quadratic Formula

by fangtray » Wed Feb 01, 2012 11:26 pm
a^2-4a+5=0

solve for a.

I know if we use the quadratic formula, we can see that there is no answer. However, this question factors easily into (a-5)(a+1). ON the exam, how will we know if an equation can factor with an answer or not? Will we need to test the quadratic formula on everything?
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by Anurag@Gurome » Wed Feb 01, 2012 11:46 pm
fangtray wrote:a^2-4a+5=0

solve for a.

I know if we use the quadratic formula, we can see that there is no answer. However, this question factors easily into (a-5)(a+1). ON the exam, how will we know if an equation can factor with an answer or not? Will we need to test the quadratic formula on everything?
a² - 4a + 5 = 0 cannot be factored as (a - 5)(a + 1). If you multiply (a - 5)(a + 1) by FOIL method, you get the expression a² - 4a - 5, which is not the case.
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