C++ program to find roots of quadratic equation ax2 + bx + c=0 (with algorithm)

Here is the C++ code to find roots of quadratic equation ax2  + bx + c=0 . It takes input for a, b and c and find the roots. You all should have in mind how it works exactly. Here is the algorithm.

  Steps

User side

1: User asked to enter values for a, b and c.

2: Screen displays disc.

3: If discernment is greater than zero Roots are real and unequal

4: If discernment is less than zero Roots are imaginary 

5: If discernment is equal to zero Roots are equal

Developer side

1: Declare variables that are going to be used in program .

2: Input variables a,b and c

3: Place an if statement to check if all are non-zero

4:  Place an if statement to check if all are positive

5: If above two conditions are true then calculate discernment using following statement disc=(b*b)-4*a*c;

6: If discernment is greater than zero Roots are real and unequal and calculated using following formulas root1=(-b+sqrtf(disc) /(2*a));

         root2=(-b-sqrtf(disc) /(2*a)); 

7: If discernment is less than zero Roots are imaginary and calculated using following formulas 

root1=sqrt(disc)<<" /"<<2*a;

root2=sqrt(disc)<<" /"<<2*a

8: If discernment is equal to zero Roots are equal and calculated using following formulas 

root1=-b/(2*a);

root2=root1;

9: Program ends here.

Here is the C++ code.

Code:

#include<iostream>

#include<math.h>

using namespace std;

void main()

{      float a,b,c;

       float disc,root1,root2;

       int i=-1;

       cout<<"Find roots of quadratic equation ax2  + bx + c=0 "<<endl<<"where a b and c are scalers"<<endl;

       cout<<"Enter value of a"<<endl;

       cin>>a;

       cout<<"Enter value of b"<<endl;

       cin>>b;

       cout<<"Enter value of c"<<endl;

       cin>>c;

       if(a==0||b==0||c==0)

              {

                     cout<<"The value cannot be zero"<<endl;

              }

       else if(a<0||b<0||c<0)

                     {

                           cout<<"Values must be greater than Zero"<<endl;

                     }

              else { disc=(b*b)-4*a*c;

                           //disc>0

                           if(disc>0)

                                  {      cout<<"disc>0 so"<<endl;

                                         cout<<"Roots are real and unequal"<<endl;

                                         root1=(-b+sqrtf(disc) /(2*a));

                                         root2=(-b-sqrtf(disc) /(2*a));

                                         cout<<"First root is = "<<root1<<endl;

                                         cout<<"Second root is = "<<root2<<endl;

                                  }

                           else //disc<0

                                  if(disc<0)

                                         {      disc=(-1)*disc;

                                                cout<<"disc<0 so"<<endl;

                                                cout<<"Roots are imaginary "<<endl;

                                                cout<<"First root=(-"<<b<<"+i*"<<sqrt(disc)<<" /"<<2*a<<")"<<endl;

                                                cout<<"Second root=(-"<<b<<"-i*"<<sqrt(disc)<<" /"<<2*a<<")"<<endl;

                                               

                                           

                                               

                                         }

                                  else { //disc=0

                                                cout<<"disc=0 so"<<endl;

                                                cout<<"Roots are equal"<<endl;

                                                root1=-b/(2*a);

                                                root2=root1;

                                                cout<<"First root is = "<<root1<<endl;

                                                cout<<"Second root is = "<<root2<<endl;

                                          }

                          

                      }

       system("pause");

}

Output: