## Equation of the sphere of radius 3 and tangent to coordinate-planes

**Problem**

Find the equation of a sphere of radius 3 and tangent to all three coordinate planes if the center is on the first octant.

A. $x^2 + y^2 + z^2 - 9 = 0$ |

B. $x^2 + y^2 + z^2 - 6x - 6y - 6z + 18 = 0$ |

C. $x^2 + y^2 + z^2 - 4x - 4y - 4z + 12 = 0$ |

D. $x^2 + y^2 + z^2 - 8x - 8y - 8z + 14 = 0$ |