# [R] How to solve following equation?

Gabor Grothendieck ggrothendieck at gmail.com
Wed Dec 3 19:20:47 CET 2008

```You don't.  This was just to make the presentation simpler.

On Wed, Dec 3, 2008 at 12:32 PM, RON70 <ron_michael70 at yahoo.com> wrote:
>
> Thanks for this reply, However I am interested to know why I need to modify
> my function to a=1?
>
> Regards,
>
>
> Gabor Grothendieck wrote:
>>
>> Assume a = 1.  If not set b = b/a, etc.
>> Now use (1) uniroot
>>
>>> f <- function(x) b + c/(1+x) + d/(1+x)^2 - 1 - x
>>> uniroot(f, 0:1)
>> \$root
>> [1] 0.8392679
>>
>> \$f.root
>> [1] 3.049818e-05
>>
>> \$iter
>> [1] 3
>>
>> \$estim.prec
>> [1] 6.103516e-05
>>
>> or multiply through by 1+x
>> and subtract 1 from both sides giving
>> x = b + c/(1+x) + d/(1+x)^2 - 1
>> and iterate that.
>>
>>> a <- b <- c <- d <- 1
>>> x <- 0
>>> for(i in 1:25) {
>> + x <- b + c/(1+x) + d/(1+x)^2 - 1
>> + print(x)
>> + }
>> [1] 2
>> [1] 0.4444444
>> [1] 1.171598
>> [1] 0.6725419
>> [1] 0.9553676
>> [1] 0.7729558
>> [1] 0.8821595
>> [1] 0.8135892
>> [1] 0.8554268
>> [1] 0.829437
>> [1] 0.8454056
>> [1] 0.835527
>> [1] 0.8416126
>> [1] 0.837854
>> [1] 0.8401717
>> [1] 0.838741
>> [1] 0.8396236
>> [1] 0.839079
>> [1] 0.839415
>> [1] 0.8392076
>> [1] 0.8393356
>> [1] 0.8392566
>> [1] 0.8393053
>> [1] 0.8392753
>> [1] 0.8392938
>>
>> On Mon, Dec 1, 2008 at 9:47 PM, RON70 <ron_michael70 at yahoo.com> wrote:
>>>
>>> I need to solve a equation like this :
>>>
>>> a = b/(1+x) + c/(1+x)^2 + d/(1+x)^3
>>>
>>> where a,b,c,d are known constant. Is there any R-way to do that?
>>>
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>>
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>>
>
> --
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>
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