计算 （a-b-c)的平方

（a-b-c)的平方
=(a-(b+c))^2
=a^2-2a(b+c)+(b+c)^2
=a^2-2ab-2ac+b^2+2bc+c^2
=a^2+b^2+c^2-2ab-2ac+2bc

a方+b方+c方-2ab-2ac+2bc

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Windows.Forms;

namespace WindowsFormsApplication4

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

double a, b, c,X,y;

a = Convert.ToInt32(textBox1.Text);

b = Convert.ToInt32(textBox2.Text);

c = Convert.ToInt32(textBox3.Text);

X = a - b - c;

y = Math.Pow(X, 2);

MessageBox.Show("y="+y);

}

}

} 照样子见一个窗体，输入代码！