/in/foo.c: In function 'main':
/in/foo.c:9:2: error: expected ';' before 'delta'
  delta=b*b-4*a*c
  ^~~~~
/in/foo.c:25:20: error: stray '\357' in program
    printf("无解")；
                    ^
/in/foo.c:25:21: error: stray '\274' in program
    printf("无解")；
                     ^
/in/foo.c:25:22: error: stray '\233' in program
    printf("无解")；
                      ^
/in/foo.c:7:12: warning: unused variable 'x2' [-Wunused-variable]
  double x1,x2;
            ^~
/in/foo.c:7:9: warning: unused variable 'x1' [-Wunused-variable]
  double x1,x2;
         ^~