#include <stdio.h>
#include <math.h>

int main(void)
{
     int a = 1 , b = 2 , c = 3;
     double w , x1 , x2 ;
     w = b*b - 4*a*c;
       if ( w > 0 )
       {
          x1=( -b + sqrt(w)) / ( 2*a );
          x2=( -b - sqrt(w)) / ( 2*a );
          printf( " 两个解 , x1=%f , x2=%f\n, "x1,x2);
       }
      
       else if ( w == 0 )
       {
            x1= (-b) / ( 2*a );
            x2=x1;
            printf ( "唯一解, x1 = x2 = %f\n, " x1 );
       }
       else
       {
             printf( "无解\n," x1,x2);
       }

return 0;
}

[color=#FF0000]# include <stdio.h>
# include <math.h>

int main (void)
{
     int a = 1 , b = 2 , c = 3;
     double w ;
     double x1 , x2 ;
     w = b*b - 4*a*c;
       if ( w > 0 )
       {
          x1=( -b + sqrt(w)) / ( 2*a );
          x2=( -b - sqrt(w)) / ( 2*a );
          printf( " 两个解 , x1=%f , x2=%f\n ",x1,x2);
       }
      
       else if ( w == 0 )
       {
            x1= (-b) / ( 2*a );
            x2=x1;
            printf ( "唯一解, x1 = x2 = %f\n", x1 );
       }
       else
       {
             printf( "无解\n", x1,x2);
       }

return 0;
}

#include <stdio.h>
#include <math.h>

int main(void)
{
     int a = 1 , b = 2 , c = 3;
     double w , x1 , x2 ;
     w = b*b - 4*a*c;
       if ( w > 0 )
       {
          x1=( -b + sqrt(w)) / ( 2*a );
          x2=( -b - sqrt(w)) / ( 2*a );
          printf( " 两个解 , x1=%f , x2=%f\n, "x1,x2);   // , 的位置不对
       }
      
       else if ( w == 0 )
       {
            x1= (-b) / ( 2*a );
            x2=x1;
            printf ( "唯一解, x1 = x2 = %f\n, " x1 );   // , 的位置不对
       }
       else
       {
             printf( "无解\n," x1,x2);// , 的位置不对   ；再就是没必要写x1，x2
       }

return 0;
}