public class wu{   public static void main(String[] args){      int a = 2,b = 1, c = 0,d = b*b-4*a*c      if (a == 0){          System.out.println("不是一元二次方程");      }      else if(a != 0){          if (d > 0){              System.out.println("有两个不等实根");          }          else if(d == 0){              System.out.println("有两个相等实根");          }          else{              System.out.println("无实根");          }      }                    }}