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Homework Help: Polynomial Division puzzler(well to me anyway :P )

  1. Feb 20, 2006 #1
    O.K I factored and reduced an equation I am doing down to (s+5t)/(t-s)

    I could not figure it out so I went to webmath and used a calculator to find out the answer so I could reverse solve the problem. The answer is 1 according to webmath. Any hints on how to get started on this becuase I do not see how you can get rid of the 5?:yuck:
     
  2. jcsd
  3. Feb 20, 2006 #2
    If it is an equation, what is the remaining part of the equation? How did you factor what you have so far?
     
  4. Feb 20, 2006 #3

    Hurkyl

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    Gold Member

    There's a very easy way to prove (s + 5t) / (t - s) is not identically equal to 1. (I'll give you time to figure this one out -- and I advise doing so, it's a widely useful but overlooked technique)


    Have you tried going through the problem a second time? I find that I rarely make the same mistake twice. So when I'm not completely confident in my arithmetic, I will often do the same problem twice from scratch (and in different ways, if possible) to check myself. If I get a mismatch, I can often track down exactly what I did wrong.


    But finally, I can't possibly figure out what you've done wrong unless you showed your work. :smile:
     
  5. Feb 20, 2006 #4
    O.k. Here goes. The equation is
    20s^2+9st+t^2 2s^2-7st+3t^2 5s^2+6st+t^2
    -------------- * --------------- * --------------
    5s^2-14st-3t^2 t^2+3st-4s^2 10s^2-3st-t^2


    factored out to

    (5s+t)(4s+t) (2s-t)(s-3t) (5s+t)(s+5t)
    ------------*-----------*-------------
    (5s+t)(s-3t) (t-s)(t+4s) (5s+t)(2s-t)

    reduced to
    (s+5t)/(t-s)
    from this point I am stuck.
     
  6. Feb 20, 2006 #5
    The numerator in your last fraction: [itex]5s^2+6st+t^2\neq(5s+t)(s+5t)[/itex].
     
  7. Feb 20, 2006 #6
    I re did the equation and ended up with (s+t)/(s-t). Thanks everyone.
     
  8. Feb 20, 2006 #7

    HallsofIvy

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    So far you haven't shown us any equation. An equation has to have a "= " somewhere in it!

    And (s+t)/(s-t) still isn't equal to 1!
     
  9. Feb 20, 2006 #8
    Sorry It was perform the indicated operation. Not solve the equation. Honestly i did not know an equation had to have a = . The instructor at the community college I am going to never spent any time on terms.
     
  10. Feb 20, 2006 #9
    As for the 1 thing. I think the calculator on webmath is messed up. It said (s+t)/(s-t) =1 But my calculator says in doing so you would have to divide by zero which cannot be done.
     
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