How to return a unaryfunction from a multi-variables function in VB.NET

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VB

i have a function define like

Public Function F(ByVal a As Double, ByVal b As Double, ByVal c As Double, ByVal x As Double) As Double
     y = ax ^ 3 + bx ^ 2 + cx + d
    Return y
   End Function

How could i creat a function allow me to read the parameter a,b,c,d and return an unary function?for example a=1,b=1,c=3,d=4

Public Function F(ByVal x As Double) As Double 
y = 1x ^ 3 + 2x ^ 2 + 3x + 4 
Return y 
End Function

or in other way how could i creat a function return a function of type

Func(Of Double,Double)