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Thread: 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.

    $\displaystyle (X+3)/4-(X-4)/2=3/8$
    $\displaystyle (2)(X+3)/4-(4)(X-4)/2=3/8$
    $\displaystyle (2x+6-4x-16)/8=3/8$
    $\displaystyle (-2X-10)/8=3/8$
    $\displaystyle 8((-2X-10)/8=3/8)$
    $\displaystyle -2x-10=3$
    $\displaystyle -2x=13$
    $\displaystyle X=7.5$
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  2. #2
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    sorry, this was wrong, check out my solution below.
    Last edited by reiward; Sep 21st 2009 at 04:12 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.

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

    $\displaystyle (2x+6-4x {\color{blue}-} 16)/8=3/8$ 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.

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

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

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

    thus removing the denominators. then it becomes

    $\displaystyle 2(x+3) - 4(x-4) = 3$

    $\displaystyle (2x+6) - (4x-16) = 3$

    $\displaystyle 2x + 6 - 4x + 16 = 3$

    $\displaystyle -2x + 22 = 3$

    $\displaystyle -2x = -19$

    $\displaystyle x = \frac {19}{2}$

    $\displaystyle x = 9.5$
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