Help Please

[Brandon33310]

I keep getting the result of nan for the x1 and x2 values, can someone please tell me what i'm doing wrong?



#include <iostream>
#include <cmath>


using namespace std;

int main()
{

/*
----------------------------------------------------
This program is by Brandon Cavendish. 9/7/2017
It will find the real roots for a quadratic equation

x1, x2 = -b+-sqrt(b^2-4ac)/2a
----------------------------------------------------
*/
// declaring variables.
double a = 0.0;
double b = 0.0;
double c = 0.0;
double x1 = 0.0;
double x2 = 0.0;
double discriminant = b * b - 4 * a * c;

x1 = -b + sqrt(discriminant) / (2 * a);
x2 = -b - sqrt(discriminant) / (2 * a);


cout << "Enter A:" << endl;
cin >> a;
cout << "Enter B:" << endl;
cin >> b;
cout << "Enter C:" << endl;
cin >> c;

cout << x1 << endl << x2;



return 0;
}

[Brandon33310]

I believe i have fixed it but i still don't believe I'm getting a correct answer.

[lastchance]

You are calculating the result before putting in the input.

You also haven't bracketed the whole of the numerator. It's only the sqrt() bit that's getting divided by 2a.

[Brandon33310]

#include <iostream>
#include <cmath>


using namespace std;

int main()
{

/*
----------------------------------------------------
This program is by Brandon Cavendish. 9/7/2017
It will find the real roots for a quadratic equation

x1, x2 = -b+-sqrt(b^2-4ac)/2a
----------------------------------------------------
*/
// declaring variables.
double a = 0.0;
double b = 0.0;
double c = 0.0;
double x1 = 0.0;
double x2 = 0.0;


cout << "Enter A:" << endl;
cin >> a;
cout << "Enter B:" << endl;
cin >> b;
cout << "Enter C:" << endl;
cin >> c;

double discriminant = b * b - 4 * a * c;

x1 = -b + (sqrt(discriminant)) / (2 * a);
x2 = -b - (sqrt(discriminant)) / (2 * a);

cout << "x1 = " << x1 << endl << "x2 = " << x2 << endl;



return 0;
}



this is the code now, i am still receiving a nan result however.

[lastchance]

#include <iostream>
#include <cmath>


using namespace std;

int main()
{
   double a = 0;0;
   double b = 0.0;
   double c = 0.0;
   double x1 = 0.0;
   double x2 = 0.0;
   
   
   cout << "Enter A:" << endl;
   cin >> a;
   cout << "Enter B:" << endl;
   cin >> b;
   cout << "Enter C:" << endl;
   cin >> c;
   
   double discriminant = b * b - 4 * a * c;
   
   if ( discriminant < 0 )                                          // Probably a good idea to check ...
   {
      cout << "Whoops! Complex roots";
   }
   else
   {
      x1 = (   -b + sqrt(discriminant)    )   / ( 2 * a );             // bracket CAREFULLY
      x2 = (   -b - sqrt(discriminant)    )   / ( 2 * a );             // bracket CAREFULLY
      cout << "x1 = " << x1 << endl << "x2 = " << x2 << endl;
   }
}

[Brandon33310]

Thank you! It's working now!

[48T7M4Gy]

http://www.cplusplus.com/forum/general/222488/ DUPLICATE