#include <bits/stdc++.h>
using namespace std;
const int MAX = 200;
int main(){
  cout << fixed << setprecision(20);
  vector<long double> fact(MAX + 1);
  fact[0] = 1;
  for (int i = 1; i <= MAX; i++){
    fact[i] = fact[i - 1] * i;
  }
  auto get = [&](int n, int k){
    if ((n + k) % 2 == 1){
      return (long double) 0;
    }
    long double a = fact[n + 1] / fact[k] / fact[n + 1 - k];
    if ((n + k) % 4 == 2){
      a *= -1;
    }
    return a;
  };
  int T;
  cin >> T;
  for (int i = 0; i < T; i++){
    int N;
    long double x;
    cin >> N >> x;
    long double s = 0;
    for (int j = N; j >= 0; j--){
      s = s * x + get(N, j);
    }
    s *= pow(x * x + 1, -(long double) N / 2);
    cout << s << endl;
  }
}