Question

c语言 求二元一次方程的根

#include<stdio.h>
#include<math.h>
int main()
{
double a,b,c,disc,x1,x2,realpart,imagpart;
scanf("%if,%if,%if",&a,&b,&c);
printf("The equation");
if(fabs(a)<=1e-6)
printf("is not a quadratic\n");
else{
disc=b*b-4*a*c;
if(fabs(disc)<=1e-6)
printf("has two equal roots:%8.4f\n",-b/(2*a));
else
if(disc>1e-6)
{
x1=(-b+sqrt(disc))/(2*a);
x2=(-b-sqrt(disc))/(2*a);
printf("has distinct real roots:%8.4f and %8.4f\n",x1,x2);
}
}
}
运行结果总是 不是二元一次方程

Answer 1

scanf("%if,%if,%if",&a,&b,&c); //double的输入格式是%lf

换成：
scanf("%lf,%lf,%lf",&a,&b,&c);

Answer 2