Anyone help me. BTW I need proper working.

The general form of the quetion of a circle is ax^2+by^2+cx+dy+e=0 where a=b=0 if the circle has a radius of three units and the center lies on the y axis which set of values of a, b, c, d, and e might correspond to the circle

Which of the following is the best first step in solving the equation below? 4+2㏒³x=17

Which equation can be used to measure the density of water in a spherical water tank? let w represent the number of water particles within the region.