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  1. #include <iostream>                    //id= 240242103
  2. #include <cmath>
  3. #include <iomanip>
  4. using namespace std;
  5.  
  6. double f(double x) {
  7.     return x*x*x - 4; // f(x) = x^3 - 4
  8. }
  9.  
  10. int main() {
  11.     double x0 = 1, x1 = 3, x2, f0, f1, f2, Ea, prev_x2;
  12.     int iterations = 3;
  13.  
  14.     cout << fixed << setprecision(6);
  15.     cout << "Iteration  x0        x1        x2        f0        f1        f2        Ea(%)\n";
  16.     cout << "----------------------------------------------------------------------------\n";
  17.  
  18.     for (int i = 1; i <= iterations; i++) {
  19.         f0 = f(x0);
  20.         f1 = f(x1);
  21.  
  22.         // False Position formula
  23.         x2 = x0 - f0*(x1 - x0)/(f1 - f0);
  24.         f2 = f(x2);
  25.  
  26.         if (i == 1)
  27.             Ea = 0;
  28.         else
  29.             Ea = fabs((x2 - prev_x2)/x2)*100;
  30.  
  31.         cout << i << "\t" << x0 << "\t" << x1 << "\t" << x2
  32.              << "\t" << f0 << "\t" << f1 << "\t" << f2 << "\t" << Ea << endl;
  33.  
  34.         // Update interval according to algorithm
  35.         if (f0*f2 < 0)
  36.             x1 = x2;
  37.         else
  38.             x0 = x2;
  39.  
  40.         prev_x2 = x2; // save x2 for next iteration
  41.     }
  42.  
  43.     cout << "\nApproximate root after " << iterations << " iterations = " << x2 << endl;
  44.     return 0;
  45. }
  46.  
Success #stdin #stdout 0.01s 5312KB
comments (?)
stdin 
Standard input is empty
stdout 
Iteration  x0        x1        x2        f0        f1        f2        Ea(%)
----------------------------------------------------------------------------
1	1.000000	3.000000	1.230769	-3.000000	23.000000	-2.135640	0.000000
2	1.230769	3.000000	1.381091	-2.135640	23.000000	-1.365689	10.884291
3	1.381091	3.000000	1.471831	-1.365689	23.000000	-0.811596	6.165064

Approximate root after 3 iterations = 1.471831
https://ideone.com/QqWbhA
language:
C++ (gcc 8.3)
created:
6 days ago
visibility:
public

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