ช่วยเฉลยการหา concave upward และ inflection point ให้หน่อยค่ะ

[flossy]

$f(x)=\frac{ln x}{\sqrt{x}}$
จงหาช่วงที่ concave upward และ inflection point

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In differential calculus and differential geometry,
an inflection point, point of inflection, flex, or inflection (British English: inflexion)
is a point on a smooth plane curve at which the curvature changes sign.

In particular, in the case of the graph of a function,
it is a point where the function changes from being concave
(concave downward) to convex (concave upward), or vice versa.