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Math Help - Laws of Exponents

  1. #1
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    Laws of Exponents

    Hello,

    First, I just want to say "Hello!" since I am new here. I am just starting my PreCal class this summer. I am a CS major, but have to take it for my degree.

    My problem is this:

    I have to express the following as a number in the form a/b, assuming a and b are integers.

    -2^4 + 3^-1

    I know that to get rid of the negative exponent I need to make it 1/3^1. However, I cannot seem to figure it out completely. Any help would be appreciated.
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by Chevytuff19 View Post
    Hello,

    First, I just want to say "Hello!" since I am new here. I am just starting my PreCal class this summer. I am a CS major, but have to take it for my degree.

    My problem is this:

    I have to express the following as a number in the form a/b, assuming a and b are integers.

    -2^4 + 3^-1

    I know that to get rid of the negative exponent I need to make it 1/3^1. However, I cannot seem to figure it out completely. Any help would be appreciated.
    You have this

    -2^4+\frac{1}{3}

    Now compute 2 to the forth power and then get a common denominator and add.
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  3. #3
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    You have this

    -2^4+\frac{1}{3}

    Now compute 2 to the forth power and then get a common denominator and add.
    I did it this way and came up with \frac{49}{3}

    I know the correct answer is \frac{47}{3} , though.

    I have tried to reverse engineer it for a while now, but can't seem to figure out exactly where I am messing it up. I am sure this is a very simple mistake I am making since I did the other questions in the same section without much trouble.

    Also, any idea why my fraction tag isn't working?
    Last edited by Chevytuff19; June 2nd 2011 at 05:44 PM. Reason: Adding info.
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  4. #4
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    Do I need to change the + sign to a - sign when I am making the exponent positive?
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  5. #5
    Behold, the power of SARDINES!
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    Quote Originally Posted by Chevytuff19 View Post
    Do I need to change the + sign to a - sign when I am making the exponent positive?
    You need to follow the order of operations. So you do exponents first

    -2^4+3^{-1} \iff -16+\frac{1}{3}

    Now you need to get a common denominator

    -16 \cdot \frac{3}{3}+\frac{1}{3}=...

    Can you finish from here?
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  6. #6
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    That makes sense now that I look at it...I forgot that {-2}^{ 4} is different than {(-2)}^{4 } . I was using 16 instead of -16. Thanks for the help!
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