HP 39gii difficulty

[lrdheat]

When integrating the equation 1/(3-x)^(2/3) in home from 0 to 3, I get the correct ~4.32674871093. The plot is symmetrical about x=3, yet I get invalid input if I integrate from 3 to 6. Why? Why the correct answer from 0 to 3, and not so for 3 to 6? I have tried various manners of entry such as 1/(3 nth root 3-x)^2 and other variants with no success.

In plot, if I take signed area under curve from 0 to 3 or from 3 to 6, I get a wild answer of 2555+.