- #1

mr_coffee

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x^2 + y^2 + z^2 = 25; x = 3;

What exactly am I suppose to do? The book doesn't show any examples of this, they just go straight into saying what an equation of a sphere is with center C(h,k.l) and radius r is (x-h)^2 +(y-k)^2 +(z-l)^1 = r^2; In particular, if the center is orgin O, then an equation of the sphere is

x^2+y^2+z^2 = r^2;

Now this looks very smilair to the above equation given, so i'm assuming its a sphere, with radius 5. But whats the x for, and how do i describe the set of points whose coordinates satisfy the given equation?> THanks