Public Class Form1
    Dim a As Integer
    Dim b As Integer
    Dim c As Integer
    Dim tmp As Integer
    Dim NB As Single
    Dim d As Integer
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label2.Text = "X²+"
        Label3.Text = "X+"
        Label4.Text = "=0"
        Label1.Text = ""
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If (TextBox1.Text = "") Or (TextBox2.Text = "") Or (TextBox3.Text = "") Then
            MsgBox("要輸入完整喔~")
            Exit Sub
        End If
        a = TextBox1.Text
        b = TextBox2.Text
        c = TextBox3.Text
        tmp = b ^ 2 - (4 * a * c)
        If tmp > 0 Then
            NB = Math.Sqrt(tmp)
            d = NB Mod 1
            If d > 0 Then
                Label1.Text = (-1 * b) & "+" & "√" & tmp & "  " & "或" & "  " & (-1 * b) & "-" & "√" & tmp & vbCrLf & "▂▂▂▂▂▂▂▂▂▂▂▂▂▂" & vbCrLf & (2 * a)
            Else
                Label1.Text = (-1 * b + NB) / (2 * a) & "  " & "或" & "  " & (-1 * b - NB) / (2 * a)
            End If
        End If
        If tmp = 0 Then
            Label1.Text = (-1 * b) / (2 * a)
        End If
        If tmp < 0 Then
            tmp = tmp * (-1)
            NB = Math.Sqrt(tmp)
            d = NB Mod 1
            If d > 0 Then
                Label1.Text = (-1 * b) & "+" & "√" & tmp & "i" & "  " & "或" & "  " & (-1 * b) & "-" & "√" & tmp & "i" & vbCrLf & "▂▂▂▂▂▂▂▂▂▂▂▂▂▂" & vbCrLf & (2 * a)
            Else
                Label1.Text = (-1 * b) & "+" & NB & "i" & "  " & "或" & "  " & (-1 * b) & "-" & NB & "i" & vbCrLf & "▂▂▂▂▂▂▂▂▂▂▂▂▂▂" & vbCrLf & (2 * a)
            End If
        End If
    End Sub
    Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
        If Char.IsDigit(e.KeyChar) Or e.KeyChar = Chr(13) Or e.KeyChar = Chr(8) Then
            e.Handled = False
        Else
            MessageBox.Show("只能輸入數字")
            e.Handled = True
        End If
    End Sub
    Private Sub TextBox2_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox2.KeyPress
        If Char.IsDigit(e.KeyChar) Or e.KeyChar = Chr(13) Or e.KeyChar = Chr(8) Then
            e.Handled = False
        Else
            MessageBox.Show("只能輸入數字")
            e.Handled = True
        End If
    End Sub
    Private Sub TextBox3_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox3.KeyPress
        If Char.IsDigit(e.KeyChar) Or e.KeyChar = Chr(13) Or e.KeyChar = Chr(8) Then
            e.Handled = False
        Else
            MessageBox.Show("只能輸入數字")
            e.Handled = True
        End If
    End Sub
End Class