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January 23rd, 2009, 05:18 PM  #1 
Newbie Joined: Jan 2009 Posts: 3 Thanks: 0  THIS QUESTION IS DRIVING ME CRAZY.. PLZ HELP !!
CONSIDER THE POINTS 'P' SUCH THAT THE DISTANCE FROM P TO A(1,5,3) IS TWICE THE DISTANCE FROM P TO B(6,2,2). SHOW THAT THE SET OF ALL SUCH POINTS IS A SPHERE, AND FIND ITS CENTER AND RADIUS. THANK YOU 
January 24th, 2009, 05:59 AM  #2 
Member Joined: Sep 2007 Posts: 30 Thanks: 0  Re: THIS QUESTION IS DRIVING ME CRAZY.. PLZ HELP !!
1) Write equation for distance from P to A in terms of x,y,z 2) Write equation for distance from P to B in terms of x,y,z 3) Combine the equations knowing the first equation equals 2 times the second equation. 4) Reduce this equation to a form that is similar to the equation of a sphere and you will have your answer. The key is reducing the equation in step 4 to squares of x,y and z independently. 
January 25th, 2009, 11:28 AM  #3 
Newbie Joined: Jan 2009 Posts: 3 Thanks: 0  Re: THIS QUESTION IS DRIVING ME CRAZY.. PLZ HELP !!
Thank you,, but steps 1 and 2 seem kind of vague... should i create the equation in terms of a parameter t,, or just by using the formula to calculate the distance, or position vector?

January 25th, 2009, 12:33 PM  #4 
Global Moderator Joined: Dec 2006 Posts: 19,291 Thanks: 1683 
Use the standard formula for the distance between two points in terms of their coordinates.


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