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The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4)

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excelingmat
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The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   Updated on: 03 Dec 2015, 05:45
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The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4)

A) 8/(1-x^8)
B) 4x/(1+x^2)
C) 4/(1-x^6)
D) 4/(1+x^4)
E) 4x/(1-x^4)
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A

Originally posted by excelingmat on 10 Oct 2015, 21:40.
Last edited by ENGRTOMBA2018 on 03 Dec 2015, 05:45, edited 2 times in total.
Corrected the question and updated the topic name
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GMATinsight
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   Updated on: 13 Oct 2015, 21:47
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excelingmat wrote:
The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1-x^6)

A) 8/(1-x^8)
B) 4x/(1+x^2)
C) 4/(1-x^6)
D) 4/(1+x^4)
E) 4x/(1-x^4)



Highlighted part has mistake as the exponent of x must be 4 in last term

CORRECT QUESTION IS "The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) = ?"

Solution is as mentioned below...
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Originally posted by GMATinsight on 11 Oct 2015, 07:26.
Last edited by GMATinsight on 13 Oct 2015, 21:47, edited 1 time in total.
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vdm
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   13 Oct 2015, 20:01
Hi GMATinsight,

In the last step, how did you change from (1-x^4) to (1+x^4)? The final answer should be 8/ (1-x^4)^2 right?
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   13 Oct 2015, 21:51
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vdm wrote:
Hi GMATinsight,

In the last step, how did you change from (1-x^4) to (1+x^4)? The final answer should be 8/ (1-x^4)^2 right?


Hi vdm,

There were two mistakes in the question as per the answer given. I took note of both but rectified one all throughout and second one on the last step. I have amde correction now.
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   03 Dec 2015, 04:46
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GMATinsight wrote:
excelingmat wrote:
The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1-x^6)

A) 8/(1-x^8)
B) 4x/(1+x^2)
C) 4/(1-x^6)
D) 4/(1+x^4)
E) 4x/(1-x^4)



Highlighted part has mistake as the exponent of x must be 4 in last term

CORRECT QUESTION IS "The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) = ?"

Solution is as mentioned below...


Hi,
yeah you are correct...
one more way that could get the answer in the type of eqn and choices given is to substitute some value for x...
0 would be better as the eq has constant term free of term 'x'..
the Eq gives us 8 as the ans , as also only choice A..
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   03 Dec 2015, 05:46
GMATinsight wrote:
vdm wrote:
Hi GMATinsight,

In the last step, how did you change from (1-x^4) to (1+x^4)? The final answer should be 8/ (1-x^4)^2 right?


Hi vdm,

There were two mistakes in the question as per the answer given. I took note of both but rectified one all throughout and second one on the last step. I have amde correction now.


GMATinsight, thank you for the corrections. I have updated the question.
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SKSSanjayChandra
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   03 Dec 2015, 10:10
Alternatively, substitute x=2 and check. Only Option A works.
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   07 Jul 2021, 23:31
Since there are no constraints mentioned on the value of 'x' in the question, apart from the obvious fact that the denominator shouldn't be zero, so substitute x = 0, in the question as well as the options and see which one matches
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rohan19
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   07 Jul 2021, 23:33
SKSSanjayChandra wrote:
Alternatively, substitute x=2 and check. Only Option A works.

Or even better would be to substitute x = 0
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink] New post   07 Apr 2023, 09:56
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Re: The value of 1/(1-x) + 1/(1+x) + 2/(1+x^2) + 4/(1+x^4) [#permalink]
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