I'm assuming

By the quotient rule, the derivative

is
Answer:
-1
Step-by-step explanation:
The total number of minus signs is odd, so the product is negative.
(-1)^39 = -(1^39) = -1
Answer:
obtuse,right,acute
Step-by-step explanation:
they are all real
Answer:
Yes there is, and it is 4.99.
Step-by-step explanation:
The constant of proportionality (let's call it
) will relate the number of books bought
and their cost
in the following way:


For the 12 books:

And for the 21 books:

The
for the two purchases is the same, thus there is a constant of proportionality between the two purchases.
P.S:
is the price per book.