Function PosFal(Tol As Double, A As Double, B As Double) As Double

    Dim Indice As Long
    Dim Error, C As Double
    
    Indice = 0
    Error = 100
    Do While Error > Tol
        
        If Indice > 100000 Then
            Exit Do
        End If
        
        C = B - fu(B) * (B - A) / (fu(B) - fu(A))
        
        If Abs(fu(C)) < Tol Then
            PosFal = C
            Error = Abs(fu(C))
            
        ElseIf fu(A) * fu(C) < 0 Then
            B = C
        
        ElseIf fu(C) * fu(B) < 0 Then
            A = C
        Else
            MsgBox "El intervalo no es correcto"
            Exit Do
        End If
                
        Indice = Indice + 1
    Loop
    
    MsgBox "Número de iteraciones es " + Str(Indice)

    

End Function