text: # Thread: Math HELP! bugging me
  
  1. ## Math HELP! bugging me
  
  What am I doing wrong here? I have applied the chain rule, but the answer is actually 92/9.
  
  2. ## Re: Math HELP! bugging me
  
  How do you set up the chain rule?
  
  And where is 92/9 coming from? I keep getting -184/9.
  
  3. ## Re: Math HELP! bugging me
  
  $\displaystyle \frac{dy}{dx}= \frac{dy}{du}\frac{du}{dx} = 10u\frac{du}{dx}+3\frac{du}{dx}=10\frac{18}{x^2+5} \frac{-36x}{(x^2+5)^2}+ 3\frac{-36x}{(x^2+5)^2}= \frac{-6480x}{(x^2+5)^3} -\frac{108x}{(x^2+5)^2}$
  
  phys251 is right.
  
  Plugging in x=2 gives -184/9.
  
  4. ## Re: Math HELP! bugging me
  
  Thanks guys, it appears I forgot to multiply 3 by the "u" prime..
  
  Anyways, I think the back of the textbook is wrong because im getting -184/9 aswell.