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Math Help - Finding other value (substitue) of Simultaneous equations...

  1. #1
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    Finding other value (substitue) of Simultaneous equations...

    Well ime really stuck and have a test tommrow...

    i know how to solve the first part like takeaway one equation from another to give the value of x or y, its the last bit finding the other value...

    my teacher says "substitution" he puts the value into the equation, i get mixed up here... what does he do, please describe to me... What is "Substitution" in maths?





    3x + y = 7
    3x - y = 5


    So i take them away giving me x = 2, then i dont know how to get the y, i dont know what my teacher means when he mixes it in with the equation...


    thanks for taking ur time to help me, apprantly the last bit is the easiest too lol


    (i know about timing the equations and signs too so ime okay there)
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  2. #2
    GAMMA Mathematics
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    Plug x = 2 back into either one of the equations. That is substitution. Solve for y.
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  3. #3
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    plugged in

    Quote Originally Posted by colby2152 View Post
    Plug x = 2 back into either one of the equations. That is substitution. Solve for y.

    i plugged it in, then do i solve like a normal equation?
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  4. #4
    GAMMA Mathematics
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    Quote Originally Posted by xAlanxEnglandx View Post
    i plugged it in, then do i solve like a normal equation?
    Yes, as in:

     3x + y = 7

     3(2) + y = 7

     y = 1
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