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Need help

  1. Jan 14, 2006 #1
    I am doing this worksheet where I have to graph the following,

    1.

    A. x=-3
    B. y=-1
    C. x-y=2
    D.x+y=6

    2.

    A. y=x
    B.y=-x
    C.y=2x-6
    D.y=-1/2x-6

    I know you don't do the homework for other people, but could you show me how to do these please?
     
  2. jcsd
  3. Jan 14, 2006 #2

    HallsofIvy

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    Here's the important hint: every one of those functions is linear. Each graph is a straight line. Two points determine a straight line. Determine the y value for two different values of x, plot the points, draw the line throught those two points.

    For example, in 1c) when x= 1, the equation x-y= 2 becomes 1- y= 2. What is y? when x= 0, the equation becomes 0-y= 2. What is y?

    Don't forget that an equation means exactly what it says. For 1b) the equation is y= -1 which doesn't have an x in it! When x= 0, what is y? When x= 1, what is y?

    The one "hard" one is the very first: 1a) x= -3. Since you are told that x must be -3, it makes no sense to ask "if x= 0, what is y?" But you can do it the other way around: When y= 0, what is x? Plot that point. When y= 1, what is x? Plot that point. Draw the line through those points.
     
  4. Jan 15, 2006 #3
    I do not quite understood what you said, HallsofIvy. Could you give some more detail or can anyone else help me?
     
  5. Jan 15, 2006 #4

    arildno

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    For ALL these exercises, you are to plot ALL points in the x,y-plane satisfying the given equation (ideally, that is).

    Taking the first:
    If you plot ALL points in the x,y-plane whose x-coordinates are all equal to -3 (that's what the equation requries), and no other points, what sort of curve do you end up with?
     
  6. Jan 16, 2006 #5

    HallsofIvy

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    What DO you know how to do? Can you graph a single point?

    Take a look at x- y= 2. When x= 0 what is y? Can you plot that point: (0, __)? When y= 0 what is x? Can you graph that point: (__, 0)?

    If you can do that, draw the line through those two points.
     
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