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-   -   Substitution with a fraction (https://www.askmehelpdesk.com/showthread.php?t=56228)

  • Jan 21, 2007, 12:39 AM
    Adderb
    Substitution with a fraction
    y = -x/2
    2x - 3y = -7

    I have reached this point:

    2x - 3(-x/2) = -7

    Can someone help me? Thanks!
  • Jan 21, 2007, 01:30 AM
    Capuchin
    Okay, the next step is to expand the brackets:

    2x + 3x/2 = -7

    then collect similar terms

    7x/2 = -7 ---> 7x = -14

    x = -2

    you can use this value for x to work out y, using one of your initial equations.

    Then you can use the other equation to check if your values are correct.

    Hope this helps
  • Jan 22, 2007, 01:31 AM
    Adderb
    Quote:

    Originally Posted by Adderb
    y = -x/2
    2x - 3y = -7

    I have reached this point:

    2x - 3(-x/2) = -7

    Can someone help me? Thanks!!

    Still confused, how did you get 7x/2 = -7
  • Jan 22, 2007, 01:33 AM
    Capuchin
    In order to add fractions, you need to give them the same denominator.
    so we convert 2x into a fraction with denominator 2

    2x = 4x/2

    putting this into your equation:

    4x/2 + 3x/2 = -7

    Now you can add the numerators:

    7x/2 = -7

    Apologies for not elaborating on this before, I did it in my head :p

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