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Homework Help: X-intercept graphing help

  1. Dec 5, 2005 #1
    I have to sketch the graph of this function:
    f(x) = x^3 + 3x^2 - 9x +5

    But how can I find the x-intercept (where y = 0) in this function?
     
  2. jcsd
  3. Dec 5, 2005 #2
    for cubic polynomials in order to find the x intercepts you need to look at hte integer factors of the constant (x^0) term
    here look at the factors of 5 they are
    +/-1,+/-5
    so find f(1), f(-1), f(5), f(-5) and determine which one is zero
    SUPPOSE (not necessarily true) f(1) = 0, then x = 1, and x-1 is a factor

    thereafter long divide the polynomial by x-1 and then you can find more intercepts easily from teh factored form.
     
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