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Math Help - Solve for an ordered pair using the substitution method

  1. #1
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    Solve for an ordered pair using the substitution method

    I'm stuck when looking for the ordered pair via the substitution method for the following equations;
    1) 8x-8y= -32
    2)9x+84 = y

    Thanks for the help...
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  2. #2
    Super Member Quacky's Avatar
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    Quote Originally Posted by jay1 View Post
    I'm stuck when looking for the ordered pair via the substitution method for the following equations;
    1) 8x-8y= -32
    2)9x+84 = y

    Thanks for the help...
    y=9x+84

    and 8y=8x+32

    Where are you stuck?
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  3. #3
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    What is the best way to find the variables?
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  4. #4
    Super Member Quacky's Avatar
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    I thought you had to use substitution?

    Here are the stages required:

    1) Divide my bottom equation by 8
    2) Substitute for y, leaving you with a single equation in terms of x
    3) Collect like terms
    4) Solve for x
    5) Resubstitute to solve for y.

    Post an attempt if you're still unable to get anywhere.
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  5. #5
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    1. x - y = -4, i.e. x + 4 = y.
    2. 9x + 84 = y
    ∴ x + 4 = 9x + 84, i.e. 8x = -80, hence x = -10.
    y = -10 + 4 = -6.
    ∴ (x, y) = (-10, -6)
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  6. #6
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    He's never going to learn if you spoon feed him answers johnny
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  7. #7
    Super Member TheChaz's Avatar
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    Quote Originally Posted by jgv115 View Post
    He's never going to learn if you spoon feed him answers johnny
    That is his modus operandi...

    http://www.mymathforum.com/viewtopic.php?f=13&t=21048

    (he changed his handle to "Neo..." for reasons that I'll let him explain)
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