C程序设计 例题 二元一次方程组（包括判断）

# include<stdio.h>
# include<math.h>
int main()
{
	double a,b,c,disc,x1,x2,p,q;
	scanf("%lf%lf%lf",&a,&b,&c);
	disc=b*b-4*a*c;
	if(disc<0)
		printf("This equation hasn't real roots\n");
	else
	{p=-b/(2.0*a);
	q=sqrt(disc)/(2.0*a);
	x1=p+q;x2=p-q;
	printf("real roots:\nx1=%7.2f\nx2=%7.2f\n",x1,x2);
	}
		return 0;
}