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  1. #include <iostream>
  2. #include <cmath>
  3.  
  4. using namespace std;
  5.  
  6. double sum(double a, int n)
  7. {
  8.     if (a != 1.0)
  9.     {
  10.         double an = pow(a,n), a1 = a - 1.0;
  11.  
  12.         return (a*a*(an-1.0)-n*a1)/(an*a1*a1);
  13.     }
  14.     else
  15.     {
  16.         return n*(n+3)/2.0;
  17.     }
  18. }
  19.  
  20. double handleSum(double a, int n)
  21. {
  22.     double t = 1.0/a;
  23.     double sum = 0.0;
  24.     for(int i = 1; i <= n; ++i, t /= a)
  25.     {
  26.         sum += (a+i)*t;
  27.     }
  28.     return sum;
  29. }
  30.  
  31. int main()
  32. {
  33.     double a;
  34.     int n;
  35.     cin >> a >> n;
  36.     cout << sum(a,n) << "  " << handleSum(a,n) << endl;
  37. }
  38.  
  39.  
Success #stdin #stdout 0.01s 5380KB
comments (?)
stdin
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2.3  22
stdout
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3.13018  3.13018
https://ideone.com/zBXyj5
language:
C++14 (gcc 8.3)
created:
1 year ago
visibility:
public

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