Question 1202119
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What is xx2?   Do you mean {{{ f(x) = x^2 + 4 }}} ?   If not, please correct and re-post. 


If you DID MEAN to write {{{ f(x) = x^2 + 4 }}} then:

f'(x) = {{{ 2x }}}
f"(x) = {{{ 2 }}}   <<< constant positive value so concave up "everywhere"
                           which of course includes [-4,6]

A.  It is not concave down at all on [-4,6]
B.  It is concave up on [-4,6]
C.  There is no inflection point on [-4,6] (or otherwise)
D.  The minimum is at x=0  (set f' = 0, solve for x)
E.  The maximum on [-4,6] occurs at x=6  (you check at the endpoints of the interval [-4,6]:  f(-4) = 20,   f(6) = 40.  Since no local maximums occur within the interval [-4,6] (rememmber it is concave up so you can only have a local minimum), there are no critical points to check on (-4,6) )