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SteelPanther


Registered: 05/28/12
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help with a pre calculus problem
#19360183 - 01/02/14 06:48 PM (10 years, 1 month ago) |
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I have been working on this for hours because to graph a certain graph I must find the zeros. I need to solve x^4 - x^2 - 6 = 0 I have tried every method of solving that I know but cannot get the correct answer of the square root of 3. I am not counting brute force as a way to solve it since I need to do this on a test with harder questions. Thanks for any help.
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Edited by SteelPanther (01/02/14 07:17 PM)
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BoldAsLove
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Re: help with a calculus problem [Re: SteelPanther] 1
#19360197 - 01/02/14 06:51 PM (10 years, 1 month ago) |
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Treat it the same way as a quadratic and factor it out. You get
(x^2-3)(x^2+2)=0
Each of the parentheses can equal zero for the equation to be true so:
x^2-3=0 and x^2+2=0
Solve those to give you four possible solutions:
x= +/- sqrt(3) and x= +/- i*sqrt(2)
Let me know if you have more questions.
Oh, and by the way, this is not calculus.
EDIT: There are other ways of solving problems like this. I can walk you through the solution using different methods if you are interested. This was simply the easiest method for this problem.
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Edited by BoldAsLove (01/02/14 06:52 PM)
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g00ru
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Re: help with a calculus problem [Re: BoldAsLove]
#19360292 - 01/02/14 07:11 PM (10 years, 1 month ago) |
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if you have a graphing calculator you can find x intercepts with that, right? ya not calculus, advanced algebra for sure.
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SteelPanther


Registered: 05/28/12
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Re: help with a calculus problem [Re: g00ru]
#19360316 - 01/02/14 07:17 PM (10 years, 1 month ago) |
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Thanks but thats just the thing, its only supposed to have a zero at +/- square root of 3 not also the sqrt of 2. The graphing calculator confirms this.
-------------------- Everything I say on here is not true, I am an insecure person who lies about doing drugs and stuff to make myself feel good. So any illegal things I may have talked about are all fictional.
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psi
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Re: help with a calculus problem [Re: SteelPanther]
#19360375 - 01/02/14 07:32 PM (10 years, 1 month ago) |
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"i" signifies the square root of negative one, an imaginary number. You only have to worry about the roots at real numbers I think.
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1620
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Re: help with a calculus problem [Re: psi]
#19360543 - 01/02/14 08:16 PM (10 years, 1 month ago) |
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^yep imaginary root
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SkeletalSpore
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Re: help with a calculus problem [Re: 1620]
#19360609 - 01/02/14 08:34 PM (10 years, 1 month ago) |
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x= i√2,-i√2,√3,-√3
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SteelPanther


Registered: 05/28/12
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Thanks, I already know about I but somehow I overlooked that it needed an I. I thought it was just +/- √2, thanks sometimes my brain and I think other peoples just act weird at times, such as when you work on an easy thing like this for 2 hours because you overlooked one small detail.
-------------------- Everything I say on here is not true, I am an insecure person who lies about doing drugs and stuff to make myself feel good. So any illegal things I may have talked about are all fictional.
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SteelPanther


Registered: 05/28/12
Posts: 3,453
Loc: The Energy
Last seen: 8 years, 24 days
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Re: help with a calculus problem [Re: SteelPanther]
#19360959 - 01/02/14 09:57 PM (10 years, 1 month ago) |
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Does anyone know if there is a simple way of solving √(x) -6 =4√x without having to write things out that take up a whole page if you were to write it normal sized.
-------------------- Everything I say on here is not true, I am an insecure person who lies about doing drugs and stuff to make myself feel good. So any illegal things I may have talked about are all fictional.
Edited by SteelPanther (01/02/14 09:58 PM)
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Shroomerited


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Re: help with a calculus problem [Re: SteelPanther] 1
#19361236 - 01/02/14 11:03 PM (10 years, 1 month ago) |
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The key to these problems is letting u=___
In your first problem, you let u=x^2. In that one, let u=x^1/4 Then you get u^2-6=u.
It's kind of cute. Both problems after the substitution are the same thing.
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SteelPanther


Registered: 05/28/12
Posts: 3,453
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Re: help with a calculus problem [Re: Shroomerited]
#19361521 - 01/03/14 12:19 AM (10 years, 1 month ago) |
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ok thanks I forgot about the u thing. This completes my 11 hours of studying I did today!
-------------------- Everything I say on here is not true, I am an insecure person who lies about doing drugs and stuff to make myself feel good. So any illegal things I may have talked about are all fictional.
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