## Determine the mean points of a circles radius and the coordinates. Help! [closed]

Show that the following definition gives a circle and determine the mean point's coordinates and radius of the circle in terms of point A and point B's coordinates.

"A circle is composed of the points P which PA / PB = a / b = K. The ratio of the distance from P to A and from P to B, two fixed points, is constant."

Cant figure this one out :/

u can see the picture at: http://i47.tinypic.com/ixdrhy.jpg

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