Let c be a real number, and consider the system of quadratic equations
y = x^2 - 9x + c,
y = 8x^2 - 13x.
For which values of c does this system have:
(a) Exactly one real solution (x,y)?
(b) More than one real solution?
(c) No real solutions?
Solutions to the quadratics are (x,y) pairs.