Given that y = M-3 / x ^ m ^ 2-8 is an inverse proportion function, then the value of M is?

Given that y = M-3 / x ^ m ^ 2-8 is an inverse proportion function, then the value of M is?

Because y is an inverse scale function, m ^ 2-8 = 1
Then M = 3 or - 3
When m = 3, M-3 = 0, rounding off
So m = - 3