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Algebra 4th power weirdness problem

  1. Nov 4, 2009 #1
    How did he get x = 2 with this equation? 4x - x^4/8 = 6

    Here's my solution:
    32x - x^4 - 48
    x( x^3 - 32 ) + 48 <---- Now I'm lost. Did he use this one? (a-b)(a^2+ab+b^2) . I tried it but can't think on what to extract.

    http://www.wolframalpha.com/input/?i=4x-x^4%2F8%3D6
     
  2. jcsd
  3. Nov 4, 2009 #2

    Mark44

    Staff: Mentor

    First off, this is an equation: 4x - x^4/8 = 6
    This is NOT an equation: 32x - x^4 - 48 -- An equation has an = sign.

    The equation is 32x - x^4 - 48 = 0, or equivalently x^4 - 32x + 48 = 0.
    This equation can be factored into (x - 2)(x^3 + 2x^2 + 4x -24) = 0.
     
  4. Nov 6, 2009 #3

    Mentallic

    User Avatar
    Homework Helper

    "He" would have probably used the rational roots theorem first, if not given any more information.
     
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