My Math Forum Finding radius and center of sphere

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 January 23rd, 2017, 06:49 PM #1 Member   Joined: Aug 2016 From: illinois Posts: 46 Thanks: 0 Finding radius and center of sphere I have the equation X^2+Y^2+Z^2-4Z+3=0. The Problem also gives the point P(1,2,3). Im not sure if i should complete the square, but im confused.
 January 23rd, 2017, 07:36 PM #2 Math Team     Joined: Jul 2011 From: Texas Posts: 2,949 Thanks: 1555 Point P(1,2,3) is not on the surface of the sphere, nor is it the sphere's center ... what does the problem specifically ask for? Thanks from romsek
January 23rd, 2017, 08:45 PM   #3
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Quote:
 Originally Posted by fivestar I have the equation X^2+Y^2+Z^2-4Z+3=0. The Problem also gives the point P(1,2,3). Im not sure if i should complete the square, but im confused.
$x^2 + y^2 + z^2 - 4z + 3 =0$

$x^2 + y^2 + (z -2)^2 =1$

This is a sphere of radius $1$ centered at $(0,0,2)$

Like Skeeter noted $(1,2,3)$ doesn't seem to have anything to do with this sphere.

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