讨论串#include <iostream>

#include <iostream> #include <cmath> using namespace std; int main (){ double s=0, n, x; cout<<"x="; cin>>x; cout<<"n="; cin>>n; for(int i=1; i<=n; i++){ s+=(i*1.0/pow(x,2*i)); } cout<<"natija="<<s; return 0; } /stdin 1 5