The general form of the equation of a circle is Ax2 + By2 + Cx + Dy + E = 0, where A = B 0. If the circle has a radius of 3 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?

a) a=0 b=0 c=2 d=2 e=3
b) a=1 b=1 c=8 d=0 e=9
c) a=1 b=1, C = 0, D = -8, and E = 7
d)

A = 1, B = 1, C = 8, D = 8, and E = 3

please help !

Question

The general form of the equation of a circle is Ax2 + By2 + Cx + Dy + E = 0, where A = B  0. If the circle has a radius of 3 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?

a) a=0 b=0 c=2 d=2 e=3
b) a=1 b=1 c=8 d=0 e=9
c) a=1 b=1, C = 0, D = -8, and E = 7
d)  

A = 1, B = 1, C = 8, D = 8, and E = 3

please help !

primeralph · Answer

Start with the general form of a circle.

hartnn · Answer

For a circle, the condition is 
a and b must be equal, and they must not be = 0 
just check these 2 conditions

primeralph · Answer

@hartnn  Not enough.

hartnn · Answer

yeah, forgot about the radius
the radius 'r' should not be imaginary, it should be a real number

anonymous · Answer

wait I'm still confused

hartnn · Answer

ok, that check was just to eliminate one of the choices. 
use, 
$(x-h)^2+
(y-k)^2 =r^2$

where, h,k is the centre of the circle 
r = radius = 3 
here, since centre lies on y axis, its x -coordinate must be 0
so, plug in h=0 
and try to simplify