c# forms problem

Question

I am making a math problem solver and one of the things it needs to solve is a Biquadratic equation, but it gives me an error (Method name expected) this is the code, could someone assist me on how to fix it? (MessageBox.Show("x1 = {0} , x2 = {1}", Math.Sqrt(D)(-c / b), -Math.Sqrt(-c / b)); <-- error comes on this line at math.sqrt)

private void button2_Click(object sender, EventArgs e)
{
if (a == 0 && b == 0 && c == 0)

{
MessageBox.Show("Every x is solution");
}
else
{
MessageBox.Show("No solution");
}
if ((-c / b < 0))
{
MessageBox.Show("No real solution");
}
else
{
MessageBox.Show("x1 = {0} , x2 = {1}", Math.Sqrt(D)(-c / b), -Math.Sqrt(-c / b));
}
}

Answer 1

* operator missing..

else
{
MessageBox.Show("x1 = {0} , x2 = {1}", Math.Sqrt(D) * (-c / b), -Math.Sqrt(-c / b));
}