c-设计语言(第五版）第五章习题答案（15）

//15.
#include<stdio.h>
#include<math.h>
int main(void)
{
 float x2 = 10, x1 = -10, x;
 float f1, f2, f3;
 for (;;)
 {
  x = (x1 + x2) / 2;
  f1 = 2 * x1*x1*x1 - 4 * x1*x1 + 3 * x1 - 6;
  f2 = 2 * x2*x2*x2 - 4 * x2 *x2 + 3 * x2 - 6;
  f3 = 2 * x*x*x - 4 * x*x + 3 * x - 6;
  if ((f1*f3) <= 0)
  {
   x2 = x;
   x = (x1 + x) / 2;

  }
  if ((f2*f3) <= 0)
  {
   x1 = x;
   x = (x2 + x) / 2;
  }
  if (fabs(x2 - x1) < pow(10, -5)) break;
 }
 printf("X=%.4f", x);
 return 0;
}