Question

Why won’t this code draw parabola? It is as simple as it can be – for every x calculate y using given function. Given y=x^2 i should draw down facing parabola with vertex in top left corner, yet it only draws some displaced dots.

private void DrawParabole(Graphics g)
    {
        for (int x = 0; x < pictureBox1.Width; x++)
        {
            g.DrawRectangle(
                Pens.Black, 
                x,
                FY(x), 
                1, 
                1
             );
        }
    }

    private int FY(int x)
    {
        int y = A*x^2 + B*x + C;
        return y;
    }

Answer 1

The reason you are getting the wrong values/scattered dots is because you are using the XOR or ^ operator instead of Math.Pow().

In order to calculate, lets say, A*x^2 you must use Math.Pow() and not ^:

int y = A*(Math.Pow(x, 2)) + B*x + C;
return y;

That should solve it for you, if it doesn’t then use this:

int y = A*(Math.Pow((double)x, 2D)) + B*x + C;
return y;

Hope this helps!