Prove that the graph of the equation
Ax2 + Cy2 + Dx + Ey + F = 0
is one of the following (except in degenerate cases).
Conic .................................................... Condition
(a) Circle .............................................. A = C, A ≠ 0
(b) Parabola .......................................... A = 0 or C = 0, but not both
(c) Ellipse ............................................. AC > 0, A ≠ C
(d) Hyperbola ........................................ AC < 0