The only reasonable "hint" is "Do it!". Take those third derivatives and put then into the equation to see if it is satisfied.
Is your difficulty with the derivative? What do you get for the first and second derivatives?
Prove It got in ahead of me again! I need to type faster!
I was asking because the third derivatives looked terrible and I thought I might be missing some theorems or properties.
It turned out that the solution is rather simple than calculating directly.
The ln function can be represented as following:
And then computing is much easier (otherwise the third derivatives looked terrible).
Thanks for the encouragement, guys!