①0 & lt； The denominator of x & ltX2 to f'(X) is greater than 0, and the quadratic function x with upward opening molecular formula is located between the two roots, of course, the quadratic function value is less than 0.

So at this time f ` (x) < 0.

② Look at the original function, because the original function contains lnx and the domain is x>, so don't consider what you said.

Note: when doing this kind of problem, it is best to find the definition domain before solving it!