1. if a is not an empty set, the equation has a solution, that is, (-3) 2-4 * a * 2 > =0, and a < =9/8.

2. If A is a unit set, the equation has only one root, that is, (-3) 2-4 * a * 2 = 0, and the solution is a=9/8.

3.a cannot be zero and cannot be solved. Because if a is 0, that is, x is 0, then 2=0. Obviously not.