I can't quite found out how to integrate this

(dx)/(x + x^(1/3))

I've tried doing it by partial fraction decomposition and u-sub x^(2/3)

Can anyone guide me to the way to solve this?

Also, how do you find K when finding out error bounds for Midpoint/Trapezoid

I know your suppose to find f''(x) but I don't get what you do after that