Circles

A   Circle with center h,k   and radius 5

       is   (x-3)^2 + (y-5)^2 = 5^2

B       (7-3)^2 + (8-5)^2 = 5^2 ?

            4^2    +    (-3)^2

              16    +       9    = 25    check!

C  Where it crosses the y-axis, x = 0   so

      (0-3)^2  + (y-5)^2 = 25

                      (y-5)^2  = 16     sqrt both sides

                         y-5  = +-4

                         y=9 and 1