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Homework Help: Calculate the inverse of f(x) = x^3 = 3x^2 + 3x -1

  1. Nov 6, 2007 #1
    f inverse for f(x)= x^3-3x^2+3x-1

    i thought of taking x common factor x(x^2-3x+3)-1
    but i got stuck with the quadratic equation !!!
  2. jcsd
  3. Nov 6, 2007 #2


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    The coefficients of x^3, x^2, x, and 1 are +1, -3, +3, -1, an interesting pattern. Can you guess a value of x that makes f(x)=0 ? Call that value x0. Then, you can divide f(x) by x-x0 using polynomial long division: http://www.purplemath.com/modules/polydiv2.htm. That will give you a quadratic that you can factorize.
  4. Nov 6, 2007 #3


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    better yet to factorise...from x^3-3x^2 is there any factor you cant take out to make it 3x-1?
  5. Nov 7, 2007 #4


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    Sorry!, please note that the rules for the Homework Help forums explicitly state that full answers should never be given to students.
  6. Nov 7, 2007 #5
    ooooh my bad. sorry about that cristo... i never saw a post about rules :eek:

    but yeah... mooneh have you ever used or heard of Pascals Triangle before it's much easier to factor than long/synthetic division etc. etc. especially for the particular function you stated... from there you just solve to get the inverse
    Last edited: Nov 7, 2007
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