# Co-ordinates

• Dec 29th 2009, 06:20 AM
BabyMilo
Co-ordinates
Quote:

The points A, B and C have Co-ordinates (5,1)(p,7)(8,2) respectively.

Quote:

Given that AB is twice the distance of AC. Calculate the possible values of p.

Thanks!
• Dec 29th 2009, 06:42 AM
$You\ have\ two\ solutions.$
$Calculate\ the\ length\ of\ AC\ using\ Pythagoras'\ theorem.$
$Then\ B\ lies\ on\ a\ circle\ of\ twice\ that\ radius.$
$The\ y\ co-ordinate\ of\ both\ points\ is\ 7.$
$Solve\ for\ the\ two\ values\ of\ x.$