Let . Find the open intervals on which is concave up (down). Then determine the -coordinates of all inflection points of .

1.   is concave up on the intervals
2.   is concave down on the intervals
3.  The inflection points occur at =

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".

In the last one, your answer should be a comma separated list of values or the word "none".

You can earn partial credit on this problem.