We have the following function:

So if we graph this function we will get the Figure below. Thus, let's study both the equation and the graph to get some conclusions. Therefore, we can assure these statements:
First. The function is defined only for

as shown in the Figure. This is also true because of

where

must be greater (or equal) than zero.
Second. The range of the function are the values of

.
Third. If

creases then

always creases, too.
(1,-10)
the 10 must be negative
reason why the others dont work:
(1,10) too positive, the other two start negative, no way is it going to be way up here
(10,1) still too high
(-1,10) then again, too high
Answer:
1) There are two definitions Charlotte came up with to define the quantity:
• Number of new subscribers divided by number of posts
• Number of new subscribers divided by number of words
2) No. The definitions have opposite results