linear-eq

//система линейных уравнений с 2мя переменными
#include <stdio.h>

void displayMessage();

int hasSolution(double a, double b, double d, double e);

double getX(double a, double b, double c, double d, double e, double f);

double getY(double a, double b, double c, double d, double e, double f);

void displaySolutions(double x, double y);


int menu();


int main() {
    double a, b, c, d, e, f;
    double x, y;
    int choice;
    displayMessage();

do
    {
        do
        {
         menu();
         scanf( "%d", &choice );
        } while (choice < 1 || choice > 3);
        switch (choice)

        {

            case 1:
                printf(  "Enter a, b, and c: " );
                scanf( "%lf", &a );
                scanf( "%lf", &b );
                scanf( "%lf", &c );
                printf(  "Enter d, e, and f: " );
                scanf( "%lf", &d );
                scanf( "%lf", &e );
                scanf( "%lf", &f );
                break;
           case 2:
                if (hasSolution(a, b, d, e))
                {
                    x = getX(a, b, c, d, e, f);
                    y = getY(a, b, c, d, e, f);
                    displaySolutions(x,y);
                }
                    else
                    {
                        printf( "The system has no solution\n" );

                    }
               break;
           case 3:
               printf(  "Thanks for using my program\n" );
        }
    } while (choice != 3);


    return 0;
}



void displayMessage(){
       printf( "This program calculates solutions to systems of linear equations of the form\n\n");
       printf( "     aX + bY = c\n" );
       printf( "     dX + eY = f\n\n" );
       return;
}

int hasSolution(double a, double b, double d, double e){
        int s;
        s=(a*e - d*b != 0);
        return s;
}


double getX(double a, double b, double c, double d, double e, double f){
        double x;
        x=(c * e - f * b) / (a * e - d * b);
        return x;
}


double getY(double a, double b, double c, double d, double e, double f){
        double  y;
        y=(a * f - d * c) / (a * e - d * b);
        return y;
}


void displaySolutions(double x, double y)
{
printf ("The solution is (%lf, %lf)\n", x, y );
return;
}

int menu()
{
            printf( "\nEnter  1 to enter a new system\n" );
            printf( "       2 to find the solution of the system\n" );
            printf( "       3 to exit\n" );
            printf( "Choice: " );
return 0;
}