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Solve this polynomial

  1. Oct 9, 2007 #1

    Bo_

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    1. The problem statement, all variables and given/known data

    P is profit in dollars of a particular mp3 player.

    P = -76x^3 + 4830x^2 - 320000, 0 < x < 60

    x is ad expense (in tens of thousands of $.) Find the smaller of two ad amounts that yield a profit of $2,500,000.



    The attempt at a solution

    All I can do is get this:

    -76x^3 + 4830x^2 - 2,820,000 = 0

    Now what do I do? I can't seem to factor. The only other way I know of is dividing by possible zeros, and I'm not feeling good about looking for the factors of 2.82 million.
     
  2. jcsd
  3. Oct 9, 2007 #2

    Dick

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    I'm pretty sure it doesn't factor. Are you sure you aren't just supposed to give an approximate answer?
     
  4. Oct 9, 2007 #3

    Bo_

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    I don't know but that'll have to do. There doesn't seem to be another way.
     
  5. Oct 9, 2007 #4
    -boo boo-
    sorry.
     
    Last edited: Oct 9, 2007
  6. Oct 9, 2007 #5
    Oh my apologies.....

    *removes post*.
     
  7. Oct 9, 2007 #6

    Dick

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    Thanks. You do get my point, right? I'm not trying to criticize your wish to help.
     
    Last edited: Oct 9, 2007
  8. Oct 10, 2007 #7
    Yea, the best I can think of is the approximate answer as well.

    I just used a brute method on my calculator to narrow it down. You may want to use a graphing calculator(available online) to see what the graph looks like at least.
     
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