一元二次方程（c语言）

# include <stdio.h>
# include <math.h>
int main(void)
{
	double a,b,c;
	double delta;
	double X1,X2;
	char ch;
	do{
		printf("请输入一元二次方程的系数:n");
		printf("a= ");
		scanf(" %lf" , &a);
		printf("b= ");
		scanf(" %lf" , &b);
		printf("c= ");
		scanf(" %lf" , &c);
		delta = b*b - 4*a*c ;
		if (delta > 0)  {
			X1 = (-b + sqrt(delta)) / (2*a);
			X1 = (-b + sqrt(delta)) / (2*a);
			printf("有两个解，x1 = %lf , x2 = %lf", X1 ,X2 );
		}else if (delta == 0){
			X1 = (-b + sqrt(delta)) / (2*a);
			printf("有两个解，x1 = x2 = %lf", X1 );
		}else {
			printf("无实数解");
		}
		printf("是否继续 (Y/N) :");
		scanf(" %c", &ch);
	} while (ch=='Y'|| ch=='y');
	return 0;
}