Let \displaystyle f(x) = \frac{1}{3x^{2}+6} . Find the open intervals on which f is concave up (down). Then determine the x -coordinates of all inflection points of f .

** Notes:**
In the first two, your answer should either be a single
interval, such as (0,1), a comma separated list of intervals, such as (-inf, 2), (3,4), or the word
"none".

1. | ||

2. | ||

3. | The inflection points occur at |

In the last one, your answer should be a comma separated list of

You can earn partial credit on this problem.