c语言高手进

以下程序出错在哪里
# include<stdio.h>

int main(void)

{
	double a, b, c;

	double detal, x1, x2;

   do {printf("a = %lf", a);

    scanf("%lf", &a);

	printf("b = %df", b);

    scanf("%lf", &b);

	printf("c =%df", c);

    scanf("%lf", &c);

	detal = b*b-4*a*c;
		if (detal > 0)

		{
			x1 = (-b - sqrt(detal))/(2*a);
		    x2 = (b - sqrt(detal))/(2*a);

			printf("有两个解: x1 = %fl,x2 = %fl", x1, x2);

		}

		else if (detal == 0)

		{
			x1 = x2 = (-b)/(2*a);

		    printf("有一个解：x1 = x2 = %lf", x1, x2);
		}


		else 

			printf("无解\n");


		printf("你想继续么？Y/X");

		scanf(" %c", &ch);
} while('y' == ch || 'Y' == ch);

return 0;

}

答案：# include<stdio.h>
#include <math.h>//1未包括头文件math.h sqrt需要

int main(void)

{
	double a, b, c;

	double detal, x1, x2;
	
	char ch;//2未定义变量ch

   do {printf("a =");//3打印a变量的值没有意义

    scanf("%lf", &a);

	printf("b =");//3

    scanf("%lf", &b);

	printf("c =");//3

    scanf("%lf", &c);

	detal = b*b-4*a*c;
		if (detal > 0)

		{
			x1 = (-b - sqrt(detal))/(2*a);
		    x2 = (b - sqrt(detal))/(2*a);

			printf("有两个解: x1 = %fl,x2 = %fl\n", x1, x2);//缺少换行符,不算错

		}

		else if (detal == 0)

		{
			x1 = x2 = (-b)/(2*a);

		    printf("有一个解：x1 = x2 = %lf\n", x1, x2);//缺少换行符,不算错
		}


		else 

			printf("无解\n");


		printf("你想继续么？Y/X");

		scanf(" %c", &ch);
} while('y' == ch || 'Y' == ch);

return 0;

}

其他：第一题： #include

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