Вычислить значение выражения

Option Strict On
Option Explicit On
Imports System.Math
Public Class Form1
    Function vvod(ByVal T As TextBox) As Integer
        Return CInt(Val(T.Text))
    End Function
    Sub vivod(ByVal Z As Double, ByVal T As TextBox)
        T.Text = CStr(Z)
    End Sub
    Private Function ST(ByVal y As Single, ByVal z As Single, ByVal x As Single) As Integer
        Return CInt(y = CSng(((3 * x ^ 3) - (4 * x ^ 2) + 2) / ((2 * x ^ 2) + (3 * x) - 1)))
        Return CInt(z = CSng((((8 * x ^ 3) + (2 * x ^ 2) + x) / ((x ^ 3) + (4 * x) - 2))))
    End Function
    Sub SA(ByVal f As Single, ByVal a As Single, ByVal b As Single, ByVal C As Single, ByVal d As Single, ByVal x As Single)
        f = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
        a = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
        b = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
        C = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
        d = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
        x = CSng(((a * x ^ 3) + (b * x ^ 2) + (C * x) + d))
    End Sub
 
    Private Sub Buttion1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim y As Integer, z As Double
        y = vvod(TextBox1) : z = vvod(TextBox2)
        vivod(y, TextBox3)
    End Sub
    Private Sub Buttion2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        End
    End Sub
End Class