Answer
An equation of the largest sphere with center (5,4,9) that
is contained in the first octant is (x-5)^2+(y-4)^2+(z-9)^2 = 16
Work Step by Step
The largest sphere contained in the first octant must have a radius equal to the minimum distance from the center (5, 4, 9) to
any of the three coordinate planes. The shortest such distance is to the XY plane, a distance of 4. Thus an equation of the
sphere is (x-5)^2+(y-4)^2+(z-9)^2 = 16
