stumped by setting integral limits

[John]

Hi, I have a function y=(x^3/2H^3+1). I am calculating flux through an area defined by this function. So I have

flux = limits (0, 2H) integral (function, dx).

This is what I cannot understand - if for the same problem, I define the flux boundary as (-H, H), the flux will become

flux = limits (-H, H) integral (function, dx)

In principle, both scenarios should result in the same result but they don't. I cannot understand what I am doing wrong.

I will appreciate any insights.

Thanks,
John.