Function Newton(ByVal Equation As String, Optional ByVal X As Variant = 0, Optional ByVal Pre As Variant = 14)

'Conversion
X = CDbl(X)
Pre = CDbl(Pre)

'Recherche de x pour que f(x)=0
Dim nb As Long, X2 As Double
Do
X2 = X
nb = nb + 1 'eviter une non convergence (boucle sans fin)
X = X - F(Equation, X) / Derive(Equation, X)
Loop Until Abs(X2 - X) < 10 ^ -Pre Or nb > 50
If nb > 50 Then
    Newton = "#NOMBRE!" 'soit divergent, soit X trop loin, soit precision insuffisante <10^-14
    Else
    Newton = X
End If

End Function