The missing factor is (a -1) I believe. If you foil (5a + 9)(a - 1) you would get 5a^2 + 4a - 9.
I am quite sure that it is B: Temperature
Answer:

Step-by-step explanation:
Using k as the constant of proportionality.
The expression that expresses the relationship : p varies jointly with the square of d and the cube of u.
Varies jointly means that p will change as 'd' and 'u' will change together with respect to their powers.
We get the expression as:

Answer:
a. is 5
c. is 3
e. is 6
b. is 1
d. is 4
f. is 2
Step-by-step explanation: