Some questions about invoking arbitrary method [closed]

package methods;
import java.lang.reflect.*;
public class MethodTableTest {
    public static void main(String[] args) throws Exception
    {
        Method square = MethodTableTest.class.getMethod("square", double.class);
        Method sqrt = Math.class.getMethod("sqrt", double.class);
        xsave(1, 10, 10, square);  
        xsave(1, 10, 10, sqrt);
    }
    public static double square(double x)
    {
        return x * x;
    }
    
    public static void xsave(double from, double to, int n, Method f)
    {
        // to print out the method as table header
        System.out.println(f);
        double dx = (to - from) / (n - 1);  
        for (double x = from; x <= to; x += dx)
        {
            try
            {
                double y = (Double) f.invoke(null, x);
                System.out.printf("%10.4f | %10.4f%n", x, y);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
        }
    }
}

Questions:

1. I do not understand why they set double dx = (to - from) / (n - 1);. What does this mean?

2. They have the for (double x = from; x <= to; x += dx). I do not understand this for loop so much.

3. The try/catch, they made the double y = (Double) f.invoke(null, x);. What does this mean? When I use google to find out the meaning of this, they said to me that it "invokes the underlying method represented by this Method object". So in this case, what does this mean?