Anyone? I'm honestly not just trying to figure out a homework problem or something. I just can never seem to find K. For this problem, I got the second derivative to be:

f'' = [ (2x^2)(x^4 + 3) ] / [ (x^4 +1)^(3/2) ]

The interval is from 0 to 1, so my understanding is that since the max value (I think) occurs at x=1, I plug in 1 for x and get my K. But that is not working. Any ideas about this problem or about finding K in general?