Circle equation:
(x-a)^2 + (y-b)^2 = r^2
x^2 - 2ax + a^2 + y^2 - 2by + b^2 = r^2
x^2 + y^2 + a^2 + b^2 - 2ax - 2by - r^2 = 0
_______________________
4x^2 + 4y^2 + 36y + 5 = 0
4x^2 + 4y^2 + 36y + 5 +0x + 0y = 0
(-2ax = 0x)
-2a = 0
a = 0
(-2by = 0y)
-2b = 0
b = 0
____________________
And now:
a^2 + b^2 - r^2 = 5
0^2 + 0^2 - r^2 = 5
0+0-r^2 = 5
r^2 = -5
Since there is no negative radius, we say that it is not an equation of a circle
