Originally Posted by helloan

Hi I'm completely new to using VB in excel, but could someone help me fix my program. I'm supposed to find the roots of the equation denoted as func using the newton raphson method. Currently I am not getting the correct roots and the range of values which can be input are very limited. Could someone help on how to fix this? Thanks!

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Option Explicit
Function newton(guess)

Dim func As Double, deriv As Double, i As Double, x2 As Double, x As Double, dif As Double

x = guess

For i = 0 To 1000
    func = x ^ 2 * Sin(x) + x ^ 3 * Exp(x) - x * Cos(x) - 7
    deriv = (x ^ 2 - 1) * Cos(x) + 3 * x * Sin(x) + (x ^ 3 + 3 * x ^ 2) * Exp(x)
    x2 = (x - func) / deriv
    dif = x2 - x
    x = x2
    If Abs(dif) < 0.001 Then i = 1000
Next i

newton = x
    
End Function

Option Explicit Function newton(guess) Dim func As Double, deriv As Double, i As Double, x2 As Double, x As Double, dif As Double x = guess For i = 0 To 1000 func = x ^ 2 * Sin(x) + x ^ 3 * Exp(x) - x * Cos(x) - 7 deriv = (x ^ 2 - 1) * Cos(x) + 3 * x * Sin(x) + (x ^ 3 + 3 * x ^ 2) * Exp(x) x2 = (x - func) / deriv dif = x2 - x x = x2 If Abs(dif) < 0.001 Then i = 1000 Next i newton = x End Function