problem with f"(x) , sorry i wrote down the wrong problem

[lblue54]

sorry i wrote down the original problem down wrong...its g(s)=s/(s+1^2) Not g(s)=s/(s+1)^2

I have been on this problem for almost an hour and i can't find where i'm messing up...i know its gotta be something simple but i'm drawing a blank...i'm going through my chapter and working all of the problems...this and another one i'm having problems with, but i figure i'm making the same mistake on both

the problem is g(s) = s/(1+s^2)

i get...

g'(s)= 1-s^2/(1+s^2)^2

here's my work for g"(s)
G"(s)= (x-1)^2(12x^3-12x^2) - (3x^4-4x^3)(2)(x-1) / (x-1)^4
=(-2s)(1+s^2)[1+s^2-(1-s^2)(-1)/(1+s^2)^3
=(-2)(1+s^2+-s^2)/(1+s^2)^3
=(-2)(2)/(1+s^2)^3
=-4s/(1+s^2)^3

if u don''t mind can u show ur work for g"(s) so i can see my mistake, thanks a

 

[Deleted member 4993]

sorry i wrote down the original problem down wrong...its g(s)=s/(s+1^2) <<<< Really??!!Not g(s)=s/(s+1)^2

I have been on this problem for almost an hour and i can't find where i'm messing up...i know its gotta be something simple but i'm drawing a blank...i'm going through my chapter and working all of the problems...this and another one i'm having problems with, but i figure i'm making the same mistake on both

the problem is g(s) = s/(1+s^2)

i get...

g'(s)= 1-s^2/(1+s^2)^2<<< I Hope you meant (1-s^2)/(1+s^2)^2

here's my work for g"(s)
G"(s)= (x-1)^2(12x^3-12x^2) - (3x^4-4x^3)(2)(x-1) / (x-1)^4<<<< where did 'x' come from - where did 's' go!! - I don't know what you are doing - you are cutting and pasting from somewhere
=(-2s)(1+s^2)[1+s^2-(1-s^2)(-1)/(1+s^2)^3<<< what happened??!!

where did ] go??!

I don't know what you are doing - you need to be careful!

=(-2)(1+s^2+-s^2)/(1+s^2)^3
=(-2)(2)/(1+s^2)^3
=-4s/(1+s^2)^3

if u don''t mind can u show ur work for g"(s) so i can see my mistake, thanks a

If I were to this problem, i would do it following way:

g'(s) = (1-s^2)/(1+s^2)^2 = U(s)/W(s)

U(s) = 1 - s^2

U'(s) = ???

W(s) = ( 1+s^2)^2

W'(s) = ???

U * W' = ???

U' * W = ???

g"(s) = (U' * W - U * W')/W^2 = ???

do it step by step - if you are still stuck, write back showing detailed work.

 

[mmm4444bot]

Hello Blue:

In the future, if you make a mistake in a post, then please use the Edit button to both correct your mistake and provide an explanation of the change(s). Alternately, you could append a new post to your original discussion (versus editing the initial post) in order to provide and explain any changes.

Creating duplicate discussions often leads to confusion and extra work for everyone involved.

Cheers,

~ Mark

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