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Math Help - Find Coordinates of Point B

  1. #1
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    Find Coordinates of Point B

    The midpoint M of line segment AB has coordinates (- 3,4). If point A is the origin, (00), what are the coordinates of point B.

    MY WORK:

    I used the distance formula to find the distance from point A to the midpoint. I found the distance to be 5 units from point A to the midpoint and of course, this means the distance to point B is 10 units. However, I was not able to find the coordinates of B. How do I find the coordinates of B without the need of graphing paper?

    I also used the midpoint formula but got no where.

    Thanks
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by magentarita View Post
    The midpoint M of line segment AB has coordinates (- 3,4). If point A is the origin, (00), what are the coordinates of point B.

    MY WORK:

    I used the distance formula to find the distance from point A to the midpoint. I found the distance to be 5 units from point A to the midpoint and of course, this means the distance to point B is 10 units. However, I was not able to find the coordinates of B. How do I find the coordinates of B without the need of graphing paper?
    hmm, ok

    I also used the midpoint formula but got no where.
    really?

    let (x,y) be the coordinates of B. then, by the midpoint formula:

    \bigg( \frac {x + 0}2, \frac {y + 0}2\bigg) = (-3,4)

    \Rightarrow \frac x2 = -3 and \frac y2 = 4
    .
    .
    .
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  3. #3
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    I see........

    Quote Originally Posted by Jhevon View Post
    hmm, ok

    really?

    let (x,y) be the coordinates of B. then, by the midpoint formula:

    \bigg( \frac {x + 0}2, \frac {y + 0}2\bigg) = (-3,4)

    \Rightarrow \frac x2 = -3 and \frac y2 = 4
    .
    .
    .
    I did not place x and y in the midpoint formula. This is why I was not able to find the coordinates of B.

    Thanks
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  4. #4
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    maybe im wrong but it looks like you dont need to use formula for this question. if you double the coordinates of the midpoint you should get point B (-6, 8)

    then use the formula to check the answer.
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