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Math Help - Plotting the intersecting point

  1. #1
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    Plotting the intersecting point

    My equation is: x+3y=4 and 2x-y=1 I need to plot the intersecting point on a graph and cannot seem to come up with the correct answer.
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  2. #2
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    Quote Originally Posted by tobiemc View Post
    My equation is: x+3y=4 and 2x-y=1 I need to plot the intersecting point on a graph and cannot seem to come up with the correct answer.
    If you're graphing these, then it's easier to convert them to the form of y=mx+b.

    So x+3y=4 -> y=-x/3+4/3 and 2x-y=1 -> y=2x-1.

    Set the two equations equal to each other and graph it.
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  3. #3
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    It is after that point I am having trouble with...

    I have gotten to this point in the equation. My teacher says I have to solve for X and then graph that and that is what I am having trouble with.
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  4. #4
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    It's not as usual to solve for x and graph it but what's the problem? Is the algebra tripping you up?
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  5. #5
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    I can't graph 4/3, it has to be a whole number so my teacher told me to solve for x instead. When I try to solve for x my answers come out wrong. Could you show me the problem worked out step by step so I can see where I am messing up.
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  6. #6
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    Quote Originally Posted by tobiemc View Post
    My equation is: x+3y=4 and 2x-y=1 I need to plot the intersecting point on a graph and cannot seem to come up with the correct answer.
    #1) x+3y=4
    x= 4-3y

    #2) 2x-y=1
    2x=1+y
    x=.5y+.5

    You have to have a fraction or decimal when solving for x, unless in the second one you solve for y.

    y=2x-1
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  7. #7
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    I graphed it as -3y on the grid, 4/1 as the slope and then graphed -1 on the grid and 2/1 as the slope. The intersect point was 1,1 but it was wrong.
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  8. #8
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    Quote Originally Posted by tobiemc View Post
    I graphed it as -3y on the grid, 4/1 as the slope and then graphed -1 on the grid and 2/1 as the slope. The intersect point was 1,1 but it was wrong.
    You are not graphing the first equation correctly. Like I said x= is not the usual form for graphing a linear equation because you don't get the immediate information of the slope and intercept. The y-int is 4/3 and the slope is -1/3.
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  9. #9
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    I am still being told that my answer is incorrect even with y-int is 4/3 and the slope is -1/3. I have no idea what I am doing wrong. Thank you so much for all your help though.
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  10. #10
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    Quote Originally Posted by tobiemc View Post
    My equation is: x+3y=4 and 2x-y=1 I need to plot the intersecting point on a graph and cannot seem to come up with the correct answer.
    Ok so we have y=(4-x)/3 and y=2x-1. Set them equal to find out the intersection point. (4-x)/3=2x-1. 4-x=6x-3 7x=7x. Plug x=1 into either equation and you get y=1. So the point is (1,1)
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  11. #11
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    It is the 4/3 that keeps stumping me. I have had no trouble being able to get a correct answer on any of my other problems but all my problems that have a fracture in them I cannot get the answer. I don't know how to plot the 4/3.
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  12. #12
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    Quote Originally Posted by tobiemc View Post
    It is the 4/3 that keeps stumping me. I have had no trouble being able to get a correct answer on any of my other problems but all my problems that have a fracture in them I cannot get the answer. I don't know how to plot the 4/3.
    Are you drawing these on a computer program or by hand? If by hand, then \frac{4}{3} is one and one-third. I would just try to get as close as possible.
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  13. #13
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    It is a computer program.
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  14. #14
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    I don't know what to tell you. I've double checked my work and I'm pretty sure I have the right answer. Maybe look in a guide online? Or call a friend who might know how to input fractions.
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  15. #15
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    Thanks for spending so much time trying to help.
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