Hello buddy.

I would say you find the derivative of (x^2 - 9)^-2 by using the chain rule

It is not!

let

Using the chain rule leads to

The derivative of -18 is "0".

If you want to find the derivative of it is by definition, so it is equal to one

-18 has no x in it, so it is a constant -> the derivative of a constant is 0

And in your example you do not need to use the product rule, because -18 is a factor of .

So the solution is

You can use the product rule -> but you need to use that [-18]' = 0.

Any more questions?

Rapha