Error 6, Overflow for Newton Rhapson

[CaraLeigh]

Hi, an overflow error keeps occurring at the step where I calculate my FX. Have tried multiple ways, anyone able to help?? This is an algoritm for the Newton Rhapson method.

Thank you.

Sub NewtonRhapsonMethod()

Dim a, E As Double      'a is the inputed initial value, E is the Accuracy(Epsilon)
Dim k, N As Integer
Dim FX, FDX, DL As Double   'FDX is the derivative of FX, FV is the functional value of the updated estimate

a = Cells(3, 7)
E = Cells(5, 7)
N = Cells(5, 8)
k = 1
Cells(2, 1) = k
Cells(2, 2) = a
a = x

Do While k <= N

FX = ((x) ^ 4) + (2 * ((x) ^ (2))) - (x) - (3)
FDX = 4 * (x) ^ 2 + 2 * (x) - 1

DL = -(FX) / (FDX)
x = x + DL
Cells(1 + k, 3) = DL
Cells(1 + k, 4) = x
Cells(1 + k, 5) = FX

If Abs(DL) <= 0 Then
    Cells(1 + k, 4).Select
    ActiveCell.Interior.ColorIndex = 36
    ActiveCell.Font.Bold = True
    Exit Sub
End If
If k > N Then
    MsgBox "Procedure is not successful"
    Exit Sub
End If
k = k + 1
Cells(1 + k, 1).Value = k
Loop
End Sub

 

[mirabeau]

I don't think you'll find this condition
If Abs(DL) <= 0 Then
being satisfied very often.

Would you like to reconsider it?