``````//**************************************
//INCLUDE files for :Equation Solver
//**************************************
#include<iostream>
#include<conio.h>
#include<cmath>
using std::cout;
using std::cin;
using std::endl;

//**************************************
// Name: Equation Solver
// Description: These program can solve first and second degree polynomial equation.
// It evens works when the roots are complex numbers(when delta is a negative value).
// By: Gonzales Cenelia
//
//
// Inputs: the coefficients of a polynomial equation
//
// Returns: the roots of the equation
//
//Assumes: None
//
//Side Effects:no side effects
//This code is copyrighted and has limited warranties.
//for details.
//**************************************

class Root
{
public:
Root() {};
~Root() {};
void pres();
void select();
double root(double a, double b);
double root_part1(double a, double b, double c, double D);
double root_part2(double a, double b, double c, double D);
};

double Root::root(double a, double b)
{
return(-b/a);
}

double Root::root_part1(double a, double b, double c, double D)
{
return sqrt(D)/(2*a);
}

double Root::root_part2(double a, double b, double c, double D)
{
return sqrt(-D)/(2*a);
}

void Root::pres()
{
cout << "=============================================================================\n";
cout << "		      Welcome to the equation solver!                                 \n";
cout << " This program can solve any first or second degree polynomial equation \n";
cout << "=============================================================================\n\n";
}

void Root::select()
{
char car = (char)254;
char exp = (char)253;
cout << car << " For solving a first degree equation \"ax + b = 0\" enter '1' or enter '2' \n";
cout << car << " for solving a second degree equation \"ax" << exp << " + bx + c = 0\": ";
}

void main()
{
Root *p = new Root;
double a = 0, b = 0, c = 0;
int choix = 1;
double D = 0, A = 0, B = 0, C = 0;
char exp = ( char )253;
while( stricmp( answer, "no" ) != 0 )
{
p->pres();
p->select();
choix = getch();
cout << endl << endl;

switch(choix)
{
case '1':
cout << "a = ";
cin  >>  a;
cout << "b = ";
cin  >>  b;

while( a == 0 )
{
cout << "\"a\" can't be 0, please choose another value: ";
cin >> a;
}

cout << "your equation is: " << a << "x + " << b << " = 0" << endl;
cout << "the solution is: x = "<< p->root( a, b ) << "\n";
break;
case '2':
cout << "a = ";
cin  >>  a;

while( a == 0 )
{
cout << "\"a\" can't be 0, please choose another value: ";
cin >> a;
}

cout << "b = ";
cin  >>  b;
cout << "c = ";
cin  >>  c;

D = b * b - ( 4 * a * c );
A = -b/( 2 * a );
cout <<"\nthe equation is: " << a << "x" << exp << " + " << b << "x + " << c << " = 0 " << endl;
cout << "\nDelta = " << D  << endl << endl;
if( D < 0 )
{
cout << "These equation have two complex roots" << endl;
cout << "the first one is: x1 = "<< A << " + " << p->root_part2( a, b, c, D ) << "i" << endl;
cout << "the second one is: x2 = "<< A << " - " << p->root_part2( a, b, c, D ) << "i" << endl;
}
else
{
cout << "These equation have two real roots" << endl;
cout << "the first one is: x1 = " << ( -b/( 2 * a ) ) + p->root_part1( a, b, c, D )  << "\n";
cout << "the second one is: x2 = " << ( -b/( 2 * a )) - p->root_part1( a, b, c, D )  << endl;
}
break;
default:
cout << "\n\nThis selection is unknown,select '1' or '2'\n";
}
cout << "\nDo you want to solve another equation ? ( Yes ) or ( No )" << endl;