Program for Polynomial Solution without Formula, Numerical Analysis

Posted by Parveen(Hoven),
Aptitude Trainer and Software Developer

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C/C++ Program for Polynomial Solution without Formula, Numerical Analysis

Determine whether the following quadratic equation has a root between -1.0 and +1.0. If it exists, print that root to an accuracy of two decimal places. Do not use the quadratic formula. The equation is: 4x² + 10x - 9 = 0

#include <iostream>
 
using namespace std;
 
int main()
{
 int counter = 0;
    
 // start from x = -1.0f
 float x = -1.0f;
 
 while(true)
 {
     // increment by 0.001
     // small steps -1.0, -.999, -.998, and so on
     x += 0.001f;
 
     // check after 100 increments
     if(counter++ == 100)
     {
         // if x has become larger than
         // 1 quit
         if(x > 1.0f)
         {
             cout << "No solution in -1 and +1";
 
             return 0;
         }
 
         // set increment counter to zero
         counter = 0;
 
     }
 
     cout << "x = " << x << endl;
 
     // caculate the equation expression
     float equation = (4 * x * x) + (10 * x) - 9;
 
     // make absolute, positive
     if(equation < 0)
     {
         equation *= -1;
     }
 
     // if it is almost zero
     // we have the solution
     if(equation < 0.01)
     {
         cout << "root = " << x << endl;
 
         break;
     }
        
 }
 
    return 0;
}

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