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Math Help - Simplifying an algebraic equation

  1. #1
    Newbie
    Joined
    Apr 2009
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    Simplifying an algebraic equation

    Hi, can someone please explain why


    simplifies to


    and not


    as I had figured out?

    I'm fully confused on it
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  2. #2
    MHF Contributor
    Joined
    Mar 2007
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    1,240

    Talking

    How would you simplify 2(x - 1) + x?

    Do the same thing here.
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  3. #3
    Junior Member
    Joined
    Mar 2009
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    58
    I think I know where you made the mistake...

    Ok, trick question: What is 3(3^{n-1})? If you answered 9^{n-1}, you made a mistake.

    Remember the rules on multiplying things with exponents with the same base?

    x^2*x is the same as x^2*x^1, of course. And since you're multiplying, you need to add the exponents. So x^2*x = x^3.

    So, in fact, 3(3^{n-1}) = 3^{n-1+1} = 3^n. Which makes your answer 3^n - 2 and definitely not 9^{n-1} - 2.

    Hope that clears it up! Easy mistake to make.
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  4. #4
    Newbie
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    Thanks guys, I understand now.
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