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Math Help - [SOLVED] More Sim Equations

  1. #1
    ADY
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    Arrow [SOLVED] More Sim Equations

    Please help with:


     X + 7Y = 6
     3X + 5Y = 14

    I still cant get my head around this!

    Thanks in advance!

    ADY
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  2. #2
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    For example multiply the first equation (both sides) by 3: 3X + 21Y = 18 and subtract from this the other equation: (3-3)X+(21-5)Y=18-14 \Leftrightarrow 16Y=4\Leftrightarrow Y=\frac {4}{16}=\boxed{\frac 14=0.25} which you can substitute in one of the original equation: X+7\cdot\frac 14=6\Leftrightarrow X=6-\frac 74=\boxed{\frac {17}4=4.25}.
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  3. #3
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    Quote Originally Posted by ADY View Post
    Please help with:


     X + 7Y = 6
     3X + 5Y = 14

    I still cant get my head around this!

    Thanks in advance!

    ADY

    3x+21y=18 -------------1

    3x+5y=14 --------------2

    2-1

    Therefore , 16y=4 , y=1/4 , then continue to solve for x .
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  4. #4
    ADY
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     <br />
x = \frac{17}{4}, y = \frac{1}{4}<br />

    ?
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  5. #5
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    Quote Originally Posted by ADY View Post
     <br />
x = \frac{17}{4}, y = \frac{1}{4}<br />

    ?
    Yeah.
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  6. #6
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    Quote Originally Posted by ADY View Post
    Please help with:


     X + 7Y = 6
     3X + 5Y = 14

    I still cant get my head around this!

    Thanks in advance!

    ADY
    try this, substitution method

     X + 7Y = 6

     3X + 5Y = 14

    x=6-7y

    3(6-7y)+5y=14

    18-21y+5y=14

    18-14=21y-5y

    4=16y

    y=\frac{1}{4}

    then substitute

    x+7y=6

    x+\frac{7}{4}=6

    x=6-\frac{7}{4}

    x=\frac{24-7}{4}

    x=\frac{17}{4}

    check

    \frac{17}{4}+7{1}{4}=6

    \frac{24}{4}=6

    6=6

    3x+5y=14

    3*\frac{17}{4}+5*\frac{1}{4}=14

    \frac{51+5}{4}=14

    \frac{56}{4}=14

    56=56

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