I have to find where y is increasing/decreasing, where it's concave up/down and any inflection points, if there are horizontal asymptotes, and then sketch it. Here's the problem:

y = x^k/1+x^k

k is a positive integer greater than one. Here's what I get for the first derivative, after that I'm stuck:

f'(x)= kx^(k-1)/(1+x^k)^2

My guess is that the function is increasing for x>o and decreasing for x<0 but stuck after that.