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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. double func(double x)
  5. {
  6.     double coeff[] = {1, 0, -4, -9};
  7.     double result = coeff[0];
  8.     for (int i = 1; i < 4; i++)
  9.         result = result * x + coeff[i];
  10.     return result;
  11. }
  12.  
  13. int main()
  14. {
  15.     double a, b, c, fa, fb, fc;
  16.  
  17.     cout << "Enter first guess a: ";
  18.     cin >> a;
  19.     cout << "Enter second guess b: ";
  20.     cin >> b;
  21.  
  22.     fa = func(a);
  23.     fb = func(b);
  24.  
  25.     if (fa * fb > 0)
  26.     {
  27.         cout << "Invalid guesses! f(a) and f(b) must have opposite signs.\n";
  28.         return 0;
  29.     }
  30.  
  31.     cout << "\n--------------------------------------------------------------\n";
  32.     cout << " Iteration" << setw(10) << "a" << setw(12) << "b"
  33.          << setw(12) << "c" << setw(14) << "f(a)" << setw(12) << "f(b)" << endl;
  34.     cout << "--------------------------------------------------------------\n";
  35.  
  36.     for (int i = 1; i <= 8; i++)
  37.     {
  38.         c = (a * fb - b * fa) / (fb - fa);
  39.         fc = func(c);
  40.  
  41.         cout << setw(6) << i << setw(14) << fixed << setprecision(6)
  42.              << a << setw(12) << b << setw(12) << c
  43.              << setw(12) << fa << setw(12) << fb << endl;
  44.  
  45.         if (fabs(fc) < 0.00001)
  46.             break;
  47.  
  48.         a = b;
  49.         fa = fb;
  50.         b = c;
  51.         fb = fc;
  52.     }
  53.  
  54.     cout << "--------------------------------------------------------------\n";
  55.     cout << "\nApproximate Root = " << fixed << setprecision(6) << c << endl;
  56.     cout << "--------------------------------------------------------------\n";
  57.  
  58.     return 0;
  59. }
  60.  
Success #stdin #stdout 0.01s 5320KB
comments (?)
stdin 
4
2
stdout 
Enter first guess a: Enter second guess b: 
--------------------------------------------------------------
 Iteration         a           b           c          f(a)        f(b)
--------------------------------------------------------------
     1      4.000000    2.000000    2.375000   39.000000   -9.000000
     2      2.000000    2.375000    2.866165   -9.000000   -5.103516
     3      2.375000    2.866165    2.681284   -5.103516    3.080613
     4      2.866165    2.681284    2.704785    3.080613   -0.448618
     5      2.681284    2.704785    2.706548   -0.448618   -0.031298
     6      2.704785    2.706548    2.706528   -0.031298    0.000360
--------------------------------------------------------------

Approximate Root = 2.706528
--------------------------------------------------------------
https://ideone.com/wn2dtm
language:
C++ (gcc 8.3)
created:
10 days ago
visibility:
public

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