Here's the question you clicked on:
5369855
How is the equation of a sphere with center at the origin similar to, and different from, the equation of a circle with center at the origin?
A sphere is just a 3D or 3 dimension version of a circle. So for a circle with center in the origin you have\[x ^{2}+y ^{2}=R ^{2}\] where R is the radius of the circle. Therefore for a sphere, we just add the 3D component or in mathematical terms, the z-axis which will give you:\[x ^{2}+y ^{2}+z ^{2}=R ^{2}\]. That's it. Peace, Love and Happiness from Puerto Rico
The z^2 as shown above makes the graph 3 dimensional and its sits on (0,0,0)
I understand it now :) Thanks for your help :)