prog3-3_.c

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<time.h>

int main(void)
{
	double x, y, z, z_max, x_max, y_max;
	srand((unsigned int) time(NULL));
	int i;
	z_max=0; x_max=0; y_max=0;
	
	for(i=0; i<1000000; i++) {
		x = ((double)rand() / RAND_MAX)*9+1;
		y = ((double)rand() / RAND_MAX)*9+1;
		
		z = x*(10+31*pow(x, -0.5)+1.3*pow(y, -0.2))-18*x
			+y*(5+15*pow(y, -0.4)+0.8*pow(x, -0.08))-10*y;
			
			/* printf("x = %f, y = %f, z = %f\n", x, y, z); */
			
			if (z >z_max){
				x_max = x;
				y_max = y;
				z_max = z;
			}
	}
	printf("x_max = %f, y_max = %f, z_max = %f\n", x_max, y_max, z_max);
}