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Given $OA=(2,9,-6)$ and $OB=(6,-3,-6)$. If $D$ is the midpoint, isit

$OD=((2+6)/2, (9-3)/2, (-6-6)/2)$?

The correct answer is


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up vote 1 down vote accepted

Your first answer is the midpoint of the line segment that joins the tip of the vector $OA$ to the tip of the vector $OB$. The one that you call the correct answer is gotten by putting the vector $AB$ into standard position with, its initial end at the origin, and then finding the midpoint.

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