/in/foo.c: In function 'main':
/in/foo.c:9:2: error: expected ';' before 'delta'
  delta=b*b-4*a*c
  ^~~~~
/in/foo.c:7:15: warning: unused variable 'x3' [-Wunused-variable]
  double x1,x2,x3;
               ^~
/in/foo.c:7:12: warning: unused variable 'x2' [-Wunused-variable]
  double x1,x2,x3;
            ^~
/in/foo.c:7:9: warning: unused variable 'x1' [-Wunused-variable]
  double x1,x2,x3;
         ^~