Find the second derivative:

$\displaystyle f(x)=x/(x^2+1)$

Thanks guys

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- Oct 8th 2006, 09:10 AMc_323_hSecond Derivative
Find the second derivative:

$\displaystyle f(x)=x/(x^2+1)$

Thanks guys - Oct 8th 2006, 09:54 AMCaptainBlack
I expect you are meant to use the quotient rule to do this, but since

I don't lnow it I will use the product rule:

df/dx= 1/(x^2+1) + x (-1)(2x)/(x^2+1)^2 = (x^2+1-2x^2)/(x^2+1)^2

.............= (1-x^2)/(x^2+1)^2

so:

d^2f/dx^2 = -2x/(x^2+1)^2 + (1-x^2) (-2) (2x)/(x^2+1)^3

..............= [-2x(x^2+1)=4x+4x^3]/(x^2+1)^3

..............= [2x(x^2=3)]/(x^2+1)^3

RonL - Oct 8th 2006, 10:07 AMc_323_h
thanks. i liked the old MHF better. what happened to latex:(

- Oct 8th 2006, 10:41 AMtopsquark