Chapter 11.1, Problem 13ES

In each part, find the standard equation of the sphere that satisfies the stated conditions.

$\begin{array}{l}\left(\text{a}\right)\text{Center}(7,1,1);\text{radius}=4.\\ \left(\text{b}\right)\text{Center}(1,0,-1);\text{diameter}=8.\\ \left(\text{c}\right)\text{Center}(-1,3,2)\text{and}\text{passing}\text{though}\text{the}\text{origin}\text{.}\\ \left(\text{d}\right)\text{A}\text{diameter}\text{has}\text{end}\text{points}(-1,2,1)\text{and}(0,2,3).\end{array}$