Solve this problem c/3 = 8

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

What is the y intercept of f(x)=(1/2)^x?

Which of the following is the explicit rule for a geometric sequence defined a recursive formula of a -5a for which the first term is 23?