How do you determine whether the function $y=ln x$ is concave up or concave down and its intervals?

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Answer 1 · 2015-08-31T16:46:09

The graph of $y = lnx$ is concave down on $(0,oo)$ .

The domain of $lnx$ is $(0,oo)$ .

The second derivative is : $-1/x^2$ which is always negative.

So the graph of $y = lnx$ is concave down on $(0,oo)$ .

How do you determine whether the function y=ln xy=ln x is concave up or concave down and its intervals?