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Math Help - simultaneous equations!!

  1. #1
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    Smile simultaneous equations!!

    please i need help with the processes of these two simultaneous equations!!:

    7x + 2y = -4
    3x + 4y = 14

    and...

    x/2 + y/3 = 5
    x/3 + y/4 = 1
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  2. #2
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    Quote Originally Posted by lauqui View Post
    please i need help with the processes of these two simultaneous equations!!:

    7x + 2y = -4
    3x + 4y = 14
    7x + 2y = -4 ...(1)
     3x + 4y = 14 ...(2)

    Working with (1)

    7x + 2y = -4

     2y = -4-7x

     y = \frac{-4}{2}-\frac{7x}{2}

    Now sub this into (2)

     3x + 4y = 14

     3x + 4 \left(\frac{-4}{2}-\frac{7x}{2}\right)= 14

    Can you find x now?
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  3. #3
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    Quote Originally Posted by lauqui View Post
    x/2 + y/3 = 5
    x/3 + y/4 = 1
    Use the same process as in my first post.

    \frac{x}{2} + \frac{y}{3} = 5 ...(1)

    \frac{x}{3} + \frac{y}{4} = 1 ...(2)

    Working on (1)

    \frac{x}{2} + \frac{y}{3} = 5

     \frac{y}{3} = 5 - \frac{x}{2}

     y = 15 - \frac{3x}{2}

    Now into (2)

    \frac{x}{3} + \frac{15 - \frac{3x}{2}}{4} = 1

    You can take it from here....

    Once you have a solution for x substittue this into either (1) or (2) to find y.
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  4. #4
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    Quote Originally Posted by lauqui View Post
    7x + 2y = -4 [1]
    3x + 4y = 14 [2]
    This is another way, known as the "elimination" process:

    Multiply [1] by -2:
    -14x - 4y = 8
    3x + 4y = 14 [2]

    Add them up:
    -11x = 22
    x = -2 ; next get y by substituting.

    Just so you have a headstart on your teacher !
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