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Math Help - Quick Check of Solving Equations?

  1. #1
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    Quick Check of Solving Equations?

    Could somone please look over this equation and check for errors.

    (X+3)/4-(X-4)/2=3/8
    (2)(X+3)/4-(4)(X-4)/2=3/8
    (2x+6-4x-16)/8=3/8
    (-2X-10)/8=3/8
    8((-2X-10)/8=3/8)
    -2x-10=3
    -2x=13
    X=7.5
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  2. #2
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    sorry, this was wrong, check out my solution below.
    Last edited by reiward; September 21st 2009 at 05:12 AM.
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  3. #3
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    Hmm..not seeing where I went wrong...

    I got a common denominator and then simplified..could you show me how you did it?
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  4. #4
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    Quote Originally Posted by EddieG View Post
    Could somone please look over this equation and check for errors.

    (X+3)/4-(X-4)/2=3/8
    (2)(X+3)/4-(4)(X-4)/2=3/8 Mr F says: You have the wrong denominators here. It should be {\color{red}(2)(X+3)/{\color{blue}8} -(4)(X-4)/{\color{blue}8} = 3/8}. The next line seems to have used the correct denominators.

    (2x+6-4x {\color{blue}-} 16)/8=3/8 Mr F says: The first mistake (excluding mistakes in setting out - see above) is in blue. The blue minus should be a plus. This will affect all that follows.

    [snip]
    ..
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  5. #5
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    Oh sorry, my mistake. My first post was wrong.

    this is my solution.

    \frac{x+3}{4} - \frac{x-4}{2} = \frac{3}{8}

    i then multiply the equation by their LCD which is 8.

    [  \frac{x+3}{4} - \frac{x-4}{2} = \frac{3}{8}  ] 8

    thus removing the denominators. then it becomes

    2(x+3) - 4(x-4) = 3

    (2x+6) - (4x-16) = 3

    2x + 6 - 4x + 16 = 3

    -2x + 22 = 3

    -2x = -19

    x = \frac {19}{2}

    x = 9.5
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