The graph of a quadratic equation in x and y can, in certain cases, be a point, a line, or a pair of lines. These are called degenerate conics. It is also possible that the equation is not satisfied by any real values of x and y. In such cases the equation has no graph; it is said to represent an imaginary conic. Each of the following represents a degenerate or imaginary conic. Where possible, sketch the graph.
(a) x2 - y2 = 0
(b) x2 + 3y2 + 7 = 0
(c) 8x2 + 7y2 = 0
(d) x2 - 2xy + y2 = 0
(e) 9x2 + 12xy + 4y2 - 52 = 0
(f) x2 + y2 - 2x - 4y = -5