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

** 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 [math] values or the word
"none".