Public Class Form1


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim x, y As Double
        x = CDbl(TextBox1.Text)
        If x < 0 Then
            Label1.Text = "ERROR"
            Return
        ElseIf x = 0 Then
            Label1.Text = CStr(0)
        Else
            y = 1 '1st guess
            While (x / y - y) > 0.00000001 Or (x / y - y) < -0.00000001
                y = (y + x / y) / 2 'next guess
            End While
            Label1.Text = CStr(y)
        End If
    End Sub



    Private Sub Label1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label1.Click
        Label1.Text = Nothing
    End Sub


End Class