大学c语言，跟着书上写的，实在不知道哪里有问题

输入x的值，使用switch语句结构编程计算下列分段函数y的值。

      3x+6， x<-10
y=    2x-4,   -10<=x<0
      8x-9,   0<=x<10
      5x+7,   x>=10



#include<stdio.h>
int main()
{
    int x,y;
    printf("please input x:");
    scanf("%d",&x);
    switch(x<10)
    {case 0: y=5*x+7;break;
     case 1: switch(x<0)
            {case 0: y=8*x-9;break;
             case 1: switch(x<-10)
                     {case 0: y=2*x-4;break;
                      case 1: y=3*x+6;break;
            }
        }
    }
    printf("x=%f,y=%f\n",x,,y);
    return 0;
}

D:\Microsoft Visual Studio\MyProjects\5654652\78788.c(8) : warning C4144: '<' : relational expression as switch expression
D:\Microsoft Visual Studio\MyProjects\5654652\78788.c(10) : warning C4144: '<' : relational expression as switch expression
D:\Microsoft Visual Studio\MyProjects\5654652\78788.c(12) : warning C4144: '<' : relational expression as switch expression

78788.obj - 0 error(s), 0 warning(s)