C语言-斐波那契数列求和!!!这里函数应该怎么写啊答:include "stdio.h"int fb(int a1, int a2, int n); //斐波那契求和函数原型申明 int main(){ int a, b, n, s;scanf("%d%d%d", &a, &b, &n);s = fb(a, b, n);printf("%d\n", s);} int fb(int a1, int a2, int n){ if(n==1)return a1;if(n==2)return a2;...