What am I doing wrong here? I have applied the chain rule, but the answer is actually 92/9.
$\displaystyle \frac{dy}{dx}= \frac{dy}{du}\frac{du}{dx} = 10u\frac{du}{dx}+3\frac{du}{dx}=10\frac{18}{x^2+5} \frac{-36x}{(x^2+5)^2}+ 3\frac{-36x}{(x^2+5)^2}= \frac{-6480x}{(x^2+5)^3} -\frac{108x}{(x^2+5)^2}$
phys251 is right.
Plugging in x=2 gives -184/9.