Solve Unknowns and Degree Equation Application

//Equation
#include<stdio.h>
#include<windows.h>
#include<math.h>

void SolveEquation2( )
{
    printf("Solve Equation Succeed!\n");
}

void SolveEquation1( )
{
    printf("Solve Equation Succeed!\n");
}

void InputDataUnk( )
{
    float a1, b1, c1, a2, b2, c2;
    float D, Dx, Dy;
    printf("Input a1, b1, c1: ");
    scanf("%f %f %f", &a1, &b1, &c1);
    printf("Input a2, b2, c2: ");
    scanf("%f %f %f", &a2, &b2, &c2);
    D=a1*b2-a2*b1;
    Dx=c1*b2-c2*b1;
    Dy=a1*c2-a2*c1;
    if (D!=0)
        printf("x=%.2f; y=%.2f", D/Dx, D/Dy);
    else
        {
            if ( (Dx!=0) || (Dy!=0) )
                printf("No solution!\n");
            if ( (Dx==0) && (Dy==0) )
                printf("Infinite solution!\n");
        }
}

void InputDataDgr( )
{
    int choice;
    float a, b, c;
    float Delta;
    printf("1.Superlative\n2.Quadratic\nInput choice: ");
    scanf("%d", &choice);
    while ( (choice!=1) && (choice!=2) )
    {
        printf("Input again: ");
        scanf("%d", &choice);
    }
    if (choice==1)
    {
        printf("Input a, b: ");
        scanf("%f %f", &a, &b);
        if (a==0)
            if (b==0) printf("Infinite solution!\n");
            else
                printf("No solution!\n");
        else printf("x=%.2f\n",-b/a);
    }
    if (choice==2)
    {
        printf("Input a, b, c: ");
        scanf("%f %f %f", &a, &b, &c);
        Delta=b*b-4*a*c;
        if (Delta==0) printf("One solution: x=%.2f\n", -b/2*a);
        if (Delta>0) printf("Two different solution: \n x1=%.2f; x2=%.2f\n", (-b - sqrt(Delta))/ 2*a , (-b + sqrt(Delta))/2 );
        if (Delta<0) printf("No solution!\n");
    }
}

int main( )
{
    int choice;
    system("cls");
    printf("1.Unknowns\n2.Degree\nInput choice: ");
    scanf("%d", &choice);
    while ( (choice!=1) && (choice!=2) )
    {
        printf("Input again: ");
        scanf("%d", &choice);
    }
    if (choice==1)
    {
        InputDataUnk( );
        SolveEquation1( );
    }
    if (choice==2)
    {
        InputDataDgr( );
        SolveEquation2( );
    }
}