第二章例2-4

#include<stdio.h>
int main(void)
{
 
 double x,y;

 printf("Enter x(x>=0):\n");
 scanf("%lf",&x);

 if(x<=15){
  y=4*x/3;
 }
 else{
  y=2.5*x-10.5;
 }
 printf("y=f(%f)=%.2f\n",x,y);

 return 0;
}