[R] newton.method

[sammyny]

Hi,
Is this method broken in R? I am using it to find roots of the following
function:
f(x) = 2.5*exp(-0.5*(2*0.045 - x)) + 2.5*exp(-0.045) + 2.5*exp(-1.5*x) - 100

It is giving an answer of -38.4762403 which is not even close (f(x) =
2.903809e+25 for x=-38.4762403). The answer should be around 0.01-0.1. This
function should converge..

Even for a simple function like  f(x) = exp(-x) * x, it gives answer as
8.89210984 for which f(x) = 0.001222392 and I set tolerance to 10^-12..

Also, is there a non graphical version of newton method? I looked at nleqslv
but have no idea how to use it..

Thanks for your help. 
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