Richard P. answered 03/17/21
PhD in Physics with 10+ years tutoring experience in STEM subjects
I think that the region boundaries must be augmented by constraints such as
x < M ; y < M for some positive real number M
In that case the x coordinate of the centroid is:
Cx = ∫ x x^7 dx / ∫ x x^7 dx with limits 0 and M
This is easily evaluated with the result Cx = (8/9 ) M
and by symmetry Cy = (8/9) M