1. The problem statement, all variables and given/known data Find an equation of the largest sphere with center (5, 4, 9) that is contained in the first octant. 2. Relevant equations x2 + y2 + z2 3. The attempt at a solution (x - 5)2 + (y - 4)2 + (z - 9)2 = R2 I am under the impression that R must be no greater than 4, is this true? My logic stems from the fact that the center is situated at (5, 4, 9), so it is only 4 units away from the y axis. If R > 4, then it will intersect the XZ plane. My textbook does not have answers, so I am not sure if my reasoning is valid.