Jordan M.

asked • 08/22/16

x^2 -x-3=0

A. Which is the best method to solve the problem?

B. What are the solutions to the problem

Neal D.

The two answers given on this page are exactly the same, just in 
different forms.
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08/23/16

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Neal D. answered • 08/22/16

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Some teachers and students prefer to complete the square to 
solve quadratics as opposed to using the quadratic formula:
 
                     X2 - X - 3 = 0
 
                         X2 - X  = 3
 
                     ( X - .5 )2 =  3 + .25
 
                 √ ( X - .5 )2 = √ 3.25
 
                         X - .5  = ± √ 3.25
 
                                X = .5 ± √ 3.25
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Michael J.

Some teachers would realize that completing square gets you the quadratic formula.  In fact, the solutions that is obtained by completing the square is in the same form as when you would use the quadratic formula.
 
 
See my files page in my profile.  It shows a step-by-step process in deriving the quadratic formula from the quadratic equation through completing the square.
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08/22/16

Neal D.

Those teachers who choose to use "completing the square" to solve the quadratic are highly aware that this is very similar 
to using the quadratic formula.  They are just as knowledgeable as any  teacher in this area.  They also know that this is
another way to solve the equation just as factoring and using the quadratic formula are other ways to do the same.
 
They also know the day is going to come when their students are going to be asked to use "completing the square" to change the equation form of quadratics, cubics, hyperbolas, and ellipses, from STANDARD FORM to GRAPHING FORM where their graphs are far more visible and easily put on the graph paper.   Sometimes, just using the easy way does not prepare the student for future work.
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08/23/16

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