Finding intervals of increase, decrease, and concavity for x/(x² - 9)

[619snake]

so... what is left now is to try to simplify and evaluate the second derivative right?

if I'm not mistaken, after simplifying, the derivative ends like this:
f"(x)=(2x(x^2 + 27))/(x^2 - 9)^3

 

[Mark44]

Yes, that looks fine.

 

[619snake]

yay! now i can sketch the graph!