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Thread: Solve by graphing

  1. #1
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    Apr 2012
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    Solve by graphing

    solve by graphing:

    x - 2y = 3
    y = 2x - 3

    How do I solve this problem? I tried using 0 for y and then 0 for x solved both then chose a third point as 1 giving me the answer x y
    0 11 /2
    -3 0
    1 -1

    when i tried to graph these 3 points it was not a straight line. any idea what I am doing wrong?

    thanks,
    Shelly

  2. #2
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    Sorry, am not understanding as of yet......

    Thank you for getting back to me, Jeff. I do understand now that I must first treat them as two seperate problems. So, correct me if I am wrong. My delimma is not understanding how to solve. As I said earlier my first attempt to solve I first let y be zero and then solve, then let x be zero and solve, then picked another number for my third point (usually, use 1) and solved. Am I wrong for attempting to solve the problem using a incorrect method? again here is my problem:

    solve the system using the graphing method:
    x - 2y = -3
    y= 2x + 1

    again you help is appreciated more than you know! I am 44 and have gone back to college, in my junior year and must pass this class. I have been out of school since 1985!!!!!!!!!!

    !I think I solved the above , I treated them as two different problems first let y be o, then x be zero, and used 1 as my last number. I now have two straight lines but they are parallel, meaning there is no solution!!!! I am pretty sure its correct!



    Quote Originally Posted by JeffM View Post
    Hi Shelly

    To determine the straight line that graphs an equation, you need to determine 2 points that satisfy the equation and so lie on the line, correct?

    If you do not understand that sentence, please say so because otherwise we going to go nowhere fast.

    If you are OK, please note that you have TWO equations. You need to graph both of them individually. That means you have to calulate two points that satisfy one equation, draw the graph for that equation, and then repeat the process for the other equation. If the two lines are different, there will either be one point or no point where they intersect. If there is a single point of intersection, that point satisfies BOTH equations because it lies on BOTH lines. Make sense now?

    (If the lines are different but do not intersect, there is no solution. If the lines are the same, every number is a solution. It is when the lines are different but intersect that there is a unique solution.)

    If you do not understanf my explanation, please ask more questions.
    Last edited by smk-67; 04-14-2012 at 08:56 PM.

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