#include<math.h>
void main()
{
double a,b,c,d,x1,x2; /*sqrt要求用double型定義用double另外double面變量間要空格*/
printf("請輸入系數a、b、c:");
scanf("%lf%lf%lf",&a,&b,&c); /*&b&c間要逗號*/
d=b*b-4*a*c;
if(d>0)
{
x1=(-b+sqrt(d))/(2*a);
x2=(-b-sqrt(d))/(2*a);
printf("x1=%.2lf\nx2=%.2lf\n",x1,x2); /*輸用%lf*/
}
else
{
printf("ERROR");
}
}