求解一元二次方程的简单c语言程序

#include <math.h>
#include <stdio.h>
main()
{
double  a, b, c, disc, x1, x2;
do
{
printf("Input  a, b, c: ");//a、b、c分别为二次项一次项常数项系数。
scanf("%lf,%lf,%lf", &a, &b, &c);
disc = b*b - 4*a*c;
if (disc < 0)
printf("disc=%lf \n Input again!\n", disc);
} while (disc<0);
printf("*******the result*******\n");
x1 = (-b+sqrt(disc))/(2*a);
x2 = (-b-sqrt(disc))/(2*a);
printf("\nx1=%6.2lf\nx2=%6.2lf\n", x1, x2);
}