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Homework Help: Solving 3rd order Polynomial

  1. Nov 16, 2004 #1
    5x^3 - 2x^2 + 3

    Where are the zeros. Is there one between [-1,1]

    THanks.
     
  2. jcsd
  3. Nov 16, 2004 #2
    There is a zero at (-0.7860031,0)
     
  4. Nov 16, 2004 #3
    Evaluate the expression at x = -1 and x = 1.

    What are the signs of the expression at these two points? What does this tell you about whether or not there is at least one root between them (hint: plot the two points and draw a line through them. Does it cross 0?) ?

    --J
     
  5. Nov 16, 2004 #4

    dduardo

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    Staff Emeritus

    UrbanXrisis, that is the wrong answer.
     
  6. Nov 16, 2004 #5
    ACK! Sorry! (-0.7290014,0) Typed in the wrong answer
     
  7. Nov 16, 2004 #6
    The easiest way to solve that for you might be to graph the equation. Then limit you window from in the x from -2 to 2 then see if it crosses the axis between -1 and 1... zoom out to see all the zeros if more exist.
     
  8. Nov 18, 2004 #7
    I think x would -0.92 if it is like this
    5x^3 - 2x^2 + 3=0
     
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