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Math Help - Finding points of intersection help for equations.

  1. #1
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    Question Finding points of intersection help for equations.

    I have two graphs:
    2x - 3y = 13

    5x + 3y = 1

    So I am assuming I need to get these two graphs in standard notation. So for the first equation; 2x - 3y = 13, I set it -3y = -2x + 13/-3 giving me y = 2/3x - 13/3.

    For the second equation 5x + 3y = 1; I set it to 3y = -5x + 1 giving me y = -5/3x + 1/3

    So the two equations I have so are

    y = 2/3x - 13/3 and
    y = -5/3x + 1/3

    So how can I find the points of intersection from these two equations?

    cheers.
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  2. #2
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    Quote Originally Posted by ipatch View Post
    I have two graphs:
    2x - 3y = 13

    5x + 3y = 1

    So I am assuming I need to get these two graphs in standard notation. So for the first equation; 2x - 3y = 13, I set it -3y = -2x + 13/-3 giving me y = 2/3x - 13/3.

    For the second equation 5x + 3y = 1; I set it to 3y = -5x + 1 giving me y = -5/3x + 1/3

    So the two equations I have so are

    y = 2/3x - 13/3 and
    y = -5/3x + 1/3

    So how can I find the points of intersection from these two equations?

    cheers.
    add the equations, term for term ...

    2x - 3y = 13

    5x + 3y = 1
    ------------
    7x = 14

    x = 2

    sub 2 for x in either equation and solve for y
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  3. #3
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    Quote Originally Posted by skeeter View Post
    add the equations, term for term ...

    2x - 3y = 13

    5x + 3y = 1
    ------------
    7x = 14

    x = 2

    sub 2 for x in either equation and solve for y
    So when I plug in x for the first equation I get x = 2 and y = -3.
    When I plug in x for the second equation I get x = 2 and y = 3.

    So with that being said, do I have two intersection points one at (2, -3) and another at (2, 3) ?

    cheers
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  4. #4
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    Quote Originally Posted by ipatch View Post
    So when I plug in x for the first equation I get x = 2 and y = -3.
    When I plug in x for the second equation I get x = 2 and y = 3. this is incorrect, try the 2nd equation again.

    So with that being said, do I have two intersection points one at (2, -3) and another at (2, 3) ?

    think! ... how can two lines intersect at more than one point?
    ...
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  5. #5
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    yeah i made a syntax error in my addition/subtraction, it is just one point. thanks for the FYI.

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