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Math Help - Can Someone Correct Me?

  1. #1
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    Can Someone Correct Me?

    a few problems I had to do for homework. Just wondering if someone could correct me?

    Directions - Simplify Expressions with Rational Exponents

    1. (8/27)^-2/3 = I got 9/4 for an answer

    2. x^1/5 / x^3/10 = my answer.....X^1/10

    3. (A^3 b^6)^1/3 = ab^2

    4. (a^2/3 b^2)^6 (a^3 b^3)^1/3 = A^5b^13

    5. (4c^5/3 / a^-1/4 b^5/6)^-3/2 = b^5/4 / 8c^5/2 a^3/8


    confusing as heck to read. I could take pictures of the problems and answers like I did yesterday but someone told me not to do that i guess?
    Last edited by mr fantastic; April 27th 2009 at 08:46 PM. Reason: ll --> ck
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  2. #2
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    Quote Originally Posted by fallenx33 View Post
    a few problems I had to do for homework. Just wondering if someone could correct me?

    Directions - Simplify Expressions with Rational Exponents

    1. (8/27)^-2/3 = I got 9/4 for an answer
    yes, your answer is right.
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  3. #3
    Member rtblue's Avatar
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    well. i know that number 3 is right. i'll have to do the others on a sheet of paper.
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  4. #4
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    Quote Originally Posted by fallenx33 View Post
    2. x^1/5 / x^3/10 = my answer.....X^1/10 x^{\frac{\color{red}-\color{black}1}{10}}
    x^{\frac{1}{5}}\div x^{\frac{3}{10}}

    =x^{\frac{1}{5}-\frac{3}{10}}

    =x^{\frac{-1}{10}}
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  5. #5
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    k so #1 is right, #3 is right.....and #2 should be x^-1/10?
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  6. #6
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    Quote Originally Posted by fallenx33 View Post
    1. (8/27)^-2/3 = I got 9/4 for an answer
    Correct.

    2. x^1/5 / x^3/10 = my answer.....X^1/10
    Not quite.

    \frac{x^{1/5}}{x^{3/10}}

    =x^{1/5-3/10}=x^{2/10-3/10}

    =x^{-1/10}=\frac1{x^{1/10}}

    We could also write it as \frac1{\sqrt[10]x}, but I think the exponential form looks better in this case (and depending on what the assignment requires, you could probably just leave it at x^{-1/10}).

    3. (A^3 b^6)^1/3 = ab^2
    Correct.

    4. (a^2/3 b^2)^6 (a^3 b^3)^1/3 = A^5b^13
    Correct.

    5. (4c^5/3 / a^-1/4 b^5/6)^-3/2 = b^5/4 / 8c^5/2 a^3/8
    Correct, assuming the b^{5/6} is supposed to be in the denominator.

    confusing as hell to read.
    Yes. I don't think you are following the normal order of operations here (at least, I did not interpret it that way). You should make liberal use of parentheses to eliminate ambiguity.

    I could take pictures of the problems and answers like I did yesterday but someone told me not to do that i guess?
    Pictures are usually a nuisance, but they are okay if that is the best you can do. I suggest becoming acquainted with \text{\LaTeX} (LaTeX); for a quick tutorial, see this post.
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  7. #7
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    Yes b^5/6 is in the denominator in #5

    and I had X1/1^10 for #2 to begin with. Should I change my answer back?
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  8. #8
    Member rtblue's Avatar
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    change your answer, so you won't confuse yourself, and write down the wrong answer instead. I think its alright if you change it.
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  9. #9
    MHF Contributor Reckoner's Avatar
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    Quote Originally Posted by fallenx33 View Post
    and I had X1/1^10 for #2 to begin with. Should I change my answer back?
    No, that is not correct under any reasonable interpretation that I can think of (but again, you are not using clear notation). Re-read my working.
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  10. #10
    Member rtblue's Avatar
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    reckoner, i am not talking about your answer. All of your answers are correct, i am talking about fallenx33's first post that started this thread. I said he should change his wrong answer there.
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  11. #11
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    Quote Originally Posted by rtblue View Post
    reckoner, i am not talking about your answer. All of your answers are correct, i am talking about fallenx33's first post that started this thread. I said he should change his wrong answer there.
    I was responding to fallenx33's post above yours. He says that he originally had "X1/1^10" (which could be interpreted any number of ways), and in his original post he has "X^1/10" (presumably meaning "x^(1/10)"), but neither of these are correct. That is what I was saying.
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