quadratic calculator to display error messages

hello i am trying to make a quadratic calculater that shows an error message or N/A when non solvable values are put in this is what i have so far but it dosent seem to be working how can i mend this?

vala = app.a.Value;

valb = app.b.Value;

valc = app.c.Value;

z1 =(-valb +sqrt(valb^2-4*vala*valc))/(2*vala);

z2 =(-valb -sqrt(valb^2-4*vala*valc))/(2*vala);

if z1 is double scalar;

app.x1.Value =z1;

else app.x1.Value ='N/A';

if z2 is double scalar

app.x2.Value =z2;

else app.x2.Value ='N/A';

Answer 1

[Monisha Nalluru]

From my understanding,

you want to display values when the roots are real and N/A in case of complex roots.

You can check whether the value is real using isreal() function

As an example

if (isreal(z1) & isreal(z2))
    app.x1.value = z1;
    app.x2.value = z2;
else
    app.x1.value = 'N/A';
    app.x2.value = 'N/A';
end