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Math Help - A (simple) System of Linear Equations

  1. #1
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    A (simple) System of Linear Equations

    I've tried the 2 methods I know (Substitution and addition) and can't get an answer to this. Some of the answers I've gotten were 7(2/5) and 22 for x. It's just been so long since I've had to one of these!

    (1/4)x - y = 7
    x + 4y = 0
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  2. #2
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    Quote Originally Posted by tyler. View Post
    I've tried the 2 methods I know (Substitution and addition) and can't get an answer to this. Some of the answers I've gotten were 7(2/5) and 22 for x. It's just been so long since I've had to one of these!

    (1/4)x - y = 7
    x + 4y = 0
    A solution using the method of addition:

    (1/4)x - y = 7 is equivalent to x - 4y = 28 (multiply the equation by 4).

    Add:
    x - 4y = 28
    x + 4y = 0
    2x = 28

    Thus, x = 14.

    Then x + 4y = 0 becomes 14 + 4y = 0; 14 = -4y; y = -14/4 = -7/2.
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  3. #3
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    Thanks for the help! I'm not sure where I went wrong with my addition... I think I may have forgotten to cancel out the 1/4 after multiplying by 4. (Although, wouldn't y = -3 1/2 at the end?)

    Thanks!
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  4. #4
    Senior Member Twig's Avatar
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     -3.5 = -\frac{7}{2}
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