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Expanding a cubic problem

  1. May 18, 2013 #1
    1. The problem statement, all variables and given/known data

    Hey

    I have a question that I have to do that involves expanding a cubic. It is given in the form y = , once it is found I have to square it and then substitute it into a formula to find the area. All I need help with is the expansion than after that it's quite easy.


    2. Relevant equations

    Sorry I don't know how to use the options here to create formulas etc. But I hope the following link works.

    https://www.physicsforums.com/attachment.php?attachmentid=58828&stc=1&d=1368927170

    This is the equation that I need to expand.


    3. The attempt at a solution

    I know how to expand a cubic already, it's not that difficult. The problem is with the +2 at the end of the equation. Do I ignore it, expand the brackets and add it on at the end?
     

    Attached Files:

  2. jcsd
  3. May 18, 2013 #2

    rock.freak667

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    Homework Helper

    Hi Grove1996,

    Usually you would do the operations in the brackets first and then simplify after. So yes you would need to add the 2 to the constant from the cubic expansion

    So when do any expansion, you would sum up all the x's and constants and so on.

    e.g. (x+1)2+4 = (x+1)(x+1) + 4 = x2 + x +x +1 +4 = x2 + 2x + 5
     
  4. May 18, 2013 #3
    Thank you :)
     
  5. May 18, 2013 #4

    Attached Files:

  6. May 18, 2013 #5
    Yes, it is correct, but you can further simplify it:

    For example:
    ## -1.5 x^4 -3 x^4 = (-1.5 - 3)x^4 = -4.5x^4 ##
     
  7. May 19, 2013 #6

    SammyS

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    Staff Emeritus
    Science Advisor
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    Gold Member

    In other words: Combine like terms.
     
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