I am having real trouble understanding this concept and I am hoping that maybe someone would be willing to help me out.

I need to find the equation for a plane that just touches the sphere (x - 2)^2 + (y - 3)^2 = (z - 3)^2 = 16 and is parallel to 1) xy plane 2) yz plane and 3) the xz plane. If someone can walk me through one of these I should be able to apply the info to the other two. Thanks very much!!!

Also, if the function (x,y,z) = x^2 + y^2 + z^2 - 2x + 3y + z I need to find a point (a,b,c) such that the function can be expressed in terms of distance from (a,b,c)

I know I need to complete the square but I am lost........

Can someone recommend a good online 3D graphing program? I need to really work on understanding what different equations look like in 3D. Thanks again, this site is WONDERFUL!