soluzione sistema lineare con visual basic

VERSION 5.00
Begin {C62A69F0-16DC-11CE-9E98-00AA00574A4F} UserForm1 
   Caption         =   "UserForm1"
   ClientHeight    =   4530
   ClientLeft      =   45
   ClientTop       =   330
   ClientWidth     =   7845
   OleObjectBlob   =   "sistema2.frx":0000
   StartUpPosition =   1  'CenterOwner
End
Attribute VB_Name = "UserForm1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit

Private Sub CommandButton1_Click()
Dim a(2), b(2), c(2) As Integer
Dim x, y As Double
Dim ds, dx, dy As Double
a(1) = TextBox1.Text
a(2) = TextBox4.Text
b(1) = TextBox2.Text
b(2) = TextBox5.Text
c(1) = TextBox3.Text
c(2) = TextBox6.Text
ds = a(1) * b(2) - a(2) * b(1)
dx = c(1) * b(2) - c(2) * b(1)
dy = a(1) * c(2) - a(2) * c(1)
Label1.Caption = "ds=" & ds
Label2.Caption = "dx=" & dx
Label3.Caption = "dy=" & dy
Select Case ds
Case Is <> 0
x = dx / ds
y = dy / ds
Label4.Caption = "x=" & x
Label5.Caption = "y=" & y
Case Is = 0
 If (dx = 0) And (dy = 0) Then
 Label4.Caption = "indeterminato"
 Else
 Label4.Caption = "impossibile"
 End If
 End Select

CommandButton2.SetFocus
End Sub

Private Sub CommandButton2_Click()
TextBox1.Text = ""
TextBox2.Text = ""
TextBox3.Text = ""
TextBox4.Text = ""
TextBox5.Text = ""
TextBox6.Text = ""
Label1.Caption = ""
Label2.Caption = ""
Label3.Caption = ""
Label4.Caption = ""
Label5.Caption = ""
TextBox1.SetFocus

End Sub

Private Sub UserForm_Click()

End Sub