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Math Help - Are my answers correct?

  1. #1
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    Are my answers correct?

    http://www.montgomeryschoolsmd.org/S.../PreCalc09.pdf

    My answers to questions 25 to 30

    25 3y+2/3y-2
    26 .1873543715
    27. -52
    28. x=3
    29. 244140625
    30. -32768(x^2y^4)
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  2. #2
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    Quote Originally Posted by yitsongg View Post
    http://www.montgomeryschoolsmd.org/S.../PreCalc09.pdf

    My answers to questions 25 to 30

    25 3y+2/3y-2 Correct
    26 .1873543715 Incorrect
    27. -52 Correct
    28. x=3 Correct, although it isn't x=3, but simply 3.
    29. 244140625 Incorrect
    30. -32768(x^2*y^4) Correct
    26 is incorrect because it is a decimal approximation. When asked to simplify, you are almost always expected to give your answers exactly (i.e. not simply plug the numbers into your calculator, but rather manipulate them by hand to get a more "simple" number. You shouldn't use a calculator at all). Given that you were able to do the other problems, I assume you can do 26 by yourself. Once you have the correct answer, re-post it and I'll check it for you.
    Last edited by RobLikesBrunch; August 27th 2009 at 02:37 PM.
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  3. #3
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    26. (3- 2)(2 3+5
    29. 125

    spaces mean breaket
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  4. #4
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    Quote Originally Posted by yitsongg View Post
    26. (3- 2)(2 3+5 Incorrect
    29. 125 Correct

    spaces mean breaket
    For 26, I assume they simply don't want the square root in the denominator (it's a bit of a pedantic simplification). So:

    \frac{3-\sqrt{2}}{2\sqrt{3}+5} \cdot \frac{2\sqrt{3}-5}{2\sqrt{3}-5} (We multiply the fraction by the conjugate of the denominator over the conjugate so we can get rid of the square root, and not get a middle term in our multiplication because the -5 and the +5 will result in a cancellation once multiplied out)

    \frac{(3-\sqrt{2})(2\sqrt{3}-5)}{-13} = \frac{(\sqrt{2}-3)(2\sqrt{3}-5)}{13}

    P.S. I apologize for saying 29 was incorrect for the wrong reason before. I hadn't looked at the question, and I misread it as an approximate decimal. But, it's correct now.
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