Find the points of inflection of the graph of the function.
The second derivative
I can see that f''(x) is undefined at 0. There is no points of inflection.
Then why doesn't the upward concave exist but does the downward concave exist?
Can anyone help me explain it?
Ah sorry, I also use that website but add inputs wrongly.
Then this one
There is no reflection points
while reading my book, I understand more about it (before that, I thought non-reflection points means non-concave upward and downward >.<)
So at x=15 f'' is undefined
Plug in 14 to f'' we get negative value=> concave downward
But I still don't understand why we have to test at the point f'' is undefined?