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What are the coordinates of point B?

  1. Sep 6, 2004 #1
    Erm, I have another problem. This question confused me, I'm not sure how to do it. Help would be apprecaited. Thanks
    The midpoint of line QS is the origin. Point Q is located in Quadrant II. What quadrant contains point S?
    Same with this one.
    M(5,12) is the midpoint of line AB. The coordinates of point A are (2,6). What are the coordinates of point B?
     
  2. jcsd
  3. Sep 6, 2004 #2
    Draw a picture. Take a point Q in the second quadrant, and draw a line from Q to the origin. Into which quadrant can you extend the line (so that it is still straight)? Now, which quadrant must S lie in?
     
  4. Sep 6, 2004 #3
    Quadrent 4 I think. Ok, I think I get it. Thanks
     
  5. Sep 7, 2004 #4

    HallsofIvy

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    In general, the midpoint of the line segment from (x0,y0) to (x1,y1) is the "average" of the two: ((x0+x1)/2, (y0+y1)/2).

    In this case you are told that the midpoint of the line segment from A:(2,6) to the point B (call its coordinates (x,y)) is (0,0). That is (2+ x)/2= 0 and (6+y)/2= 0. It should be easy to see that B is (-2, -6).
     
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