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Math Help - Math 20 linear Equations by elimination

  1. #1
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    Math 20 linear Equations by elimination

    I can't seem to get the correct answer on this one.
    Solve by elimination:
    x+2/6 - 3(y+2)/2 = 1
    x-2/2 + y-1/3 =0
    (sorry i don't know how to make fractions in html...)

    the answer is supposed to be (4,-2)
    i think i'm messing up when i try to get rid of the fractions.
    i get:
    x+9y=17 and 3x+2y=8
    i times the first one by -3 so i can cancel the x when added together and end up with 29y=65 which doesn't work.

    any takers?
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  2. #2
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    decimals as well.

    i'm having the same problem with the decimals. i have no idea how to approach this.

    0.3x-o.5=1.2
    0.7x-0.2y=-0.1
    solve by elimination yet again.

    do i change everything to fractions?
    i'm really not sure how to do this one....
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  3. #3
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    Quote Originally Posted by t-dot View Post
    I can't seem to get the correct answer on this one.
    Solve by elimination:
    x+2/6 - 3(y+2)/2 = 1
    x-2/2 + y-1/3 =0
    (sorry i don't know how to make fractions in html...)

    the answer is supposed to be (4,-2)
    i think i'm messing up when i try to get rid of the fractions.
    i get:
    x+9y=17 and 3x+2y=8
    i times the first one by -3 so i can cancel the x when added together and end up with 29y=65 which doesn't work.

    any takers?
    I am going to assume that the two equations you need solved are \frac{x+2}{6}-\frac{3(y+2)}{2}=1 and \frac{x-2}{2}+\frac{y-1}{3}=0

    I said assume because without parenthesis what you wrote implies x+\frac{2}{6}-\frac{3(y+2)}{2}=1 and x-\frac{2}{2}+y-\frac{1}{3}=0 I understand that you do not know latex and cannot write fractions, but you must be careful with order of operations and use ( ) to denote what goes with what

    Anyway...

    \frac{x+2}{6}-\frac{3(y+2)}{2}=1 and \frac{x-2}{2}+\frac{y-1}{3}=0

    Let's multiply both sides of both equations by 6, this will cancel the denominators and we'll get

    x+2-3(3(y+2))=6 and 3(x-2)+2(y-1)=0

    So x+2-9y-18=6 and 3x-6+2y-2=0

    So x-9y=6-2+18=22 and 3x+2y=8

    Can you solve x-9y=22 and 3x+2y=8?
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  4. #4
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    Quote Originally Posted by t-dot View Post
    i'm having the same problem with the decimals. i have no idea how to approach this.

    0.3x-o.5=1.2
    0.7x-0.2y=-0.1
    solve by elimination yet again.

    do i change everything to fractions?
    i'm really not sure how to do this one....
    No you do not need to change everything to fractions, all of these change to numbers very easily if we multiply both sides of both equations by 10, then we get

    3x-5=12 and 7x-2y=-1
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  5. #5
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    thanks so much i was able to get rid of everything after that
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