void div(){
    float a1=2,b1=3,c1=3;
    float a2=1,b2=5,c2=1;
    if (a2==0 or b2==0 or c2==0) {
        printf ("Divide by zero!");
        return 0;
    }
    float x,y,z;
    x=a1/a2;
    y=b1/b2;
    z=c1/c2;
    if (x!=0) {
        if (x!=1) printf ("%fx^2", x);
        else printf ("x^2");
    }
    if (y!=0) {
        if (y!=1) printf (" + %fx", y);
        else printf (" + x");
    }
    if (z!=0) printf (" + %f", z);
    printf (" = 0");
}