# related rates, chain rule problem

• Jun 22nd 2010, 09:38 AM
Red
related rates, chain rule problem
A point is moving along the graph of the given function such that $\displaystyle \frac{dx}{dt}$ is 2 centimeters per second. Find $\displaystyle \frac{dy}{dt}$ for the given values of x.

y = $\displaystyle \frac{3}{2+x^2}$

x= -2

was wondering about the differentiating, so far i have:

- $\displaystyle \frac{6x(\frac{dx}{dt})}{2+(x^2)^2}$

answer i get seems to be off though, but i'm guessing i messed up somewhere in the process.
• Jun 22nd 2010, 09:49 AM
earboth
Quote:

Originally Posted by Red
A point is moving along the graph of the given function such that $\displaystyle \frac{dx}{dt}$ is 2 centimeters per second. Find $\displaystyle \frac{dy}{dt}$ for the given values of x.

y = $\displaystyle \frac{3}{2+x^2}$

x= -2

was wondering about the differentiating, so far i have:

- $\displaystyle \frac{6x(\frac{dx}{dt})}{\bold{(}2+x^2)^2}$ <----- typo

answer i get seems to be off though, but i'm guessing i messed up somewhere in the process.

...
• Jun 22nd 2010, 09:57 AM
Red
okay, now i got the problem right.

thanks for pointing that out, i was going by this example problem and it didn't have the denominator in parenthesis because for some reason it doesn't show in the .pdf file. anyway i got the answer to my question though.