#include <stdio.h>
#include <math.h>
int main()
{
    double a,b,c,s,area;
    scanf("%lf,%lf,%lf,&a,&b，&c");
    s=1.0/2*(a+b+c);
    area=sqrt(s*(s-a)*(s-b)*(s-c));
    printf("a=%7.2lf,b=%7.2lf,c=%7.2lf,s=%7.2lf\n",a,b,c,s);
    printf("area=%7.2f\n",area);
    return 0;
}

scanf("%lf,%lf,%lf,&a,&b，&c");------- scanf("%lf,%lf,%lf",&a,&b,&c);
&a,&b,&c不能把他们放在引号内，句中还有个中文逗号，建议此句改为scanf("%lf%lf%lf",&a,&b,&c);输入数据时以空格分开

#include <stdio.h>
#include <math.h>
int main()
{
double a,b,c,x1,x2;
scanf("a=%lf,b=%lf,c=%lf",&a,&b,&c);
x1=(-b+sqrt(b*b-4*a*c))/(2*a);
x2=(-b-sqrt(b*b-4*a*c))/(2*a);
printf("x1=%5.2f,x2=%5.2f\n",x1,x2);
return 0;
}

谢谢，十分感谢，我搞了半天