方程 ax+b=0 的解：一个或无数个

Translation: When 'a=0' and 'b=0', the equation 'ax+b=0' has infinitely many solutions. When 'a≠0' and 'b≠0', the equation 'ax+b=0' has only one solution. In summary, the equation 'ax+b=0' has either one solution or infinitely many solutions.