Differentiate both sides with respect to
, using the product and chain rules on the left side.

When
, the given equation tells us that
. Then if
, it follows that

Answer:
the answer is 7 packages. I think let me know if I'm wrong
There should be a graph there to show you and I think you plot it into the graph. I might be wrong
Yes this is true, it is also referred to and known as the Reflexive property meaning pretty much that any value is equal to itself.
I hope this helps :)