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Math Help - Solving simultaneous equations using the substitution method.

  1. #1
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    Solving simultaneous equations using the substitution method.

    Thanks,
    That did help a lot. I tried doing one on my own right after, but am a little stuck.

    x-2y=4
    2x-4y=5

    I did:

    2y=4+x
    2x-4(4+x)=5

    2x-16+4x=5 ----> 6x = ?
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  2. #2
    Super Member Quacky's Avatar
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    Windsor, South-East England
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    Re: Solving Using Substitution

    Edit: Your method is littered with small errors: did you check it?

    1) x-2y=4

    2) 2x-4y=5

    From 1), x=4+2y

    Substituting this into 2):

    2(4+2y)-4y=5

    Try to solve this, and you will realize that 8\neq{5} as the original equations suggest. Do you have a typo?
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  3. #3
    Newbie mathland's Avatar
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    Nov 2011
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    Bronx, New York
    Posts
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    Re: Solving Using Substitution

    Quote Originally Posted by annon25 View Post
    Thanks,
    That did help a lot. I tried doing one on my own right after, but am a little stuck.

    x-2y=4
    2x-4y=5

    I did:

    2y=4+x
    2x-4(4+x)=5

    2x-16+4x=5 ----> 6x = ?

    Did you make up these two equations? As Quacky proved, 8 does not equal 5. Here are two more samples for you to practice.

    2x 3y = 2
    4x + y = 24



    AND the second below


    7x + 2y = 16
    21x 6y = 24
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