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February 9th, 2013, 08:38 AM   #1
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What is the correct way to apply quadratic formula?

Hello,

I have this equation which I want to solve for variable :



This is the Quadratic equation which I was taught in school:



So I substitute the a, b and c:




The problem is that Wolfram Alpha says the above is incorrect, and this is correct:



Click here to see the solution at Wolfram Alpha

I would like to learn why Wolfram Alpha is saying this. What do you think?

Thank you for your time.

Kind regards,
Marius
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February 9th, 2013, 09:13 AM   #2
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Re: What is the correct way to apply quadratic formula?

You need to put your equation in standard form first:



Now, you can see:

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February 9th, 2013, 09:59 AM   #3
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Re: What is the correct way to apply quadratic formula?

Thanks.M
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February 9th, 2013, 06:09 PM   #4
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Re: What is the correct way to apply quadratic formula?

Quote:
Originally Posted by king.oslo
Make it easier on yourself, King; let sin(h) = k, and multiply through by 2:
2y = 2vtk - gt^2
Then:
gt^2 - 2vkt + 2y = 0
Get my drift?
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February 12th, 2013, 05:28 AM   #5
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Re: What is the correct way to apply quadratic formula?

Quote:
Originally Posted by Denis
Quote:
Originally Posted by king.oslo
Make it easier on yourself, King; let sin(h) = k, and multiply through by 2:
2y = 2vtk - gt^2
Then:
gt^2 - 2vkt + 2y = 0
Get my drift?
Yes Denis, that makes sense.

I was looking at the dimensions in the result, and I cannot get them to match.





This looks right

What about this?













Everything but the one m cancel out, and I am left with:



Where did I go wrong?

Thanks M
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February 12th, 2013, 06:21 AM   #6
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You incorrectly replaced "" with "*" early on.
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February 12th, 2013, 06:34 AM   #7
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Re: What is the correct way to apply quadratic formula?

Skipjack, thank you so much! Now everything works out in my lovely mathematics

Thank you!M
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February 13th, 2013, 04:48 AM   #8
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Re: What is the correct way to apply quadratic formula?

Another question:

When I am picking , and , I have the choice to pick the inverted set of numbers, because the right hand side of the standard form is 0 anyway. Are there any implications of doing this? I think so, at least it seems that for one set of numbers I may end up with a complex number as the result, but not in the other.

For example, I suspect in the case of:



may not always be equal to in the case of:



Is this the case? If so, what is the correct way to pick the sign of , and ?

Thank you for your time.

Kind regards,
Marius
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February 13th, 2013, 05:52 AM   #9
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Re: What is the correct way to apply quadratic formula?

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February 13th, 2013, 06:02 AM   #10
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Re: What is the correct way to apply quadratic formula?

Quote:
Originally Posted by greg1313
Okay, thanks.M
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