3*3矩陣

            int[,] a = new int[4, 4];
            int[,] b = new int[4, 4];
            int[,] c = new int[4, 4];
           
            a[1,1]=int.Parse(textBox1.Text);
            a[1,2]=int.Parse(textBox4.Text);
            a[1,3]=int.Parse(textBox7.Text);
            a[2,1]=int.Parse(textBox2.Text);
            a[2,2]=int.Parse(textBox5.Text);
            a[2,3]=int.Parse(textBox8.Text);
            a[3,1]=int.Parse(textBox3.Text);
            a[3,2]=int.Parse(textBox6.Text);
            a[3,3]=int.Parse(textBox9.Text);

            b[1,1]=int.Parse(textBox10.Text);
            b[1,2]=int.Parse(textBox13.Text);
            b[1,3]=int.Parse(textBox16.Text);
            b[2,1]=int.Parse(textBox11.Text);
            b[2,2]=int.Parse(textBox14.Text);
            b[2,3]=int.Parse(textBox17.Text);
            b[3,1]=int.Parse(textBox12.Text);
            b[3,2]=int.Parse(textBox15.Text);
            b[3,3]=int.Parse(textBox18.Text);

            c[1,1]=a[1,1]*b[1,1]+a[1,2]*b[2,1]+a[1,3]*b[3,1];
            c[1,2]=a[1,1]*b[1,2]+a[1,2]*b[2,2]+a[1,3]*b[3,2];
            c[1,3]=a[1,1]*b[1,3]+a[1,2]*b[2,3]+a[1,3]*b[3,3];
            c[2,1]=a[2,1]*b[1,1]+a[2,2]*b[2,1]+a[2,3]*b[3,1];
            c[2,2]=a[2,1]*b[1,2]+a[2,2]*b[2,2]+a[2,3]*b[3,2];
            c[2,3]=a[2,1]*b[1,3]+a[2,2]*b[2,3]+a[2,3]*b[3,3];
            c[3,1]=a[3,1]*b[1,1]+a[3,2]*b[2,1]+a[3,3]*b[3,1];
            c[3,2]=a[3,1]*b[1,2]+a[3,2]*b[2,2]+a[3,3]*b[3,2];
            c[3,3]=a[3,1]*b[1,3]+a[3,2]*b[2,3]+a[3,3]*b[3,3];

            textBox19.Text=""+c[1,1];
            textBox22.Text=""+c[1,2];
            textBox25.Text=""+c[1,3];
            textBox20.Text=""+c[2,1];
            textBox23.Text=""+c[2,2];
            textBox26.Text=""+c[2,3];
            textBox21.Text=""+c[3,1];
            textBox24.Text=""+c[3,2];
            textBox27.Text=""+c[3,3];