I'll assume the equation given to you is

Please let me know if this assumption is incorrect. If so, then I'll make a correction.
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We must complete the square for each variable x, y, and z.

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The template
represents a sphere centered at (a,b,c) and has radius r.
The final equation in the previous section matches the template perfectly, which confirms we have a sphere.
We see that:
Therefore, the sphere
is centered at (x,y,z) = (1,2,-4) and has radius r = 6.