I am having trouble with the power rule on derivatives. I understand that 1/x^5 is x^-5, but what about something like 16/x^2? The problem I'm working is square root x^3 - x^2 +16/x^2. With points (4, -7)

The way I am incorrrectly working it is 3x^1/2 - 2x + 16/2x^-1.