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Expansion help.

  1. Mar 24, 2009 #1
    Can someone help me.

    How would you expand or factor out an-1

    Is there a theorem for this?
  2. jcsd
  3. Mar 24, 2009 #2
    is it a^(n-1) or (a^n)-1?
  4. Mar 25, 2009 #3
  5. Mar 25, 2009 #4


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    Science Advisor

    It's a pretty well known formula:

    [tex]a^n- 1= (a-1)(a^{n-1}+ a^{n-2}+ \cdot\cdot\cdot+ a^2+ a+ 1)[/tex]
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