#include using namespace std; /* SYNTAX: "x n" BOTH VALUES MUST BE INTEGERS X HAS TO BE BIGGER THAN N FORMULA: 1 + 2!/(x - 2) - 3!/(x - 3) + 4!/(x - 4) ... n!/(x-n) IDEA BY: Jake https://www.sololearn.com/Profile/14120873/?ref=app MADE BY: .--. _ : .; ::_; : :.-..--. .--. .--. .--. : :: :: :: ..': ..'' '_.'' '_.' :_;:_;:_;:_; :_; `.__.'`.__.' May 18, 2019 15:20 */ //CALCULATE FACTORIAL double factorial(int n) { if (n == 1) { return 1; } else { return n * factorial(n - 1); } } int main() { double result = 1; double now; int x; int n; //GET USER INPUT OF X AND N cout << "Please key in x value: "; cin >> x; cout << x << "\n"; cout << "Please key in n value: "; cin >> n; cout << n << "\n\n\n"; if (x > n) { //CALCULATE RESULT for (int i = 2; i <= n; i++) { //CALCULATE ONE CHUCK (LIKE 2!/8-2) now = factorial(i) / (x - i); //EVERY SECOND CHUCK SHOULD BE SUBTRACTED FROM THE RESULT if (i % 2 == 0) { result += now; } else { result -= now; } } //DISPLAY cout << "Result = 1 + "; for (int i = 2; i <= n; i++) { if (i == 2) { cout << i << "!/" << x - i; } else if (i % 2 == 0) { cout << " + " << i << "!/" << x - i; } else { cout << " - " << i << "!/" << x - i; } } cout << " = " << result; } else { //IF N IS BIGGER THAN X cout << "Wrong input, x value must be greater than n!"; } return 0; }

First C++ program