用C语言回答，急，大家帮个忙

刚开始学C语言，没想到高数里也有这个东西，就做不出来了，根本没有丝路

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

double first_order_precession_difference(double x, double h) {
    return (exp(x + h) - exp(x)) / h;
}

double first_order_posterior_difference(double x, double h) {
    return (exp(x) - exp(x - h)) / h;
}

double first_order_midpoint_difference(double x, double h) {
    return (exp(x + h) - exp(x - h)) / (h * 2);
}

int main() {
    double x = 0.0;
    for (int i = 0; i <= 6; i++) {
        double h = pow(0.5, i);
        printf("h = %lf\n", h);
        double r1 = first_order_precession_difference(x, h);
        double r2 = first_order_posterior_difference(x, h);
        double r3 = first_order_midpoint_difference(x, h);
        printf("前差：%lf\n后差：%lf\n中差：%lf\n", r1, r2, r3);
    }
    return 0;
}