Answer:
B. -21a-15
Step-by-step Explanation:

Answer: D
Step-by-step explanation:
(5z + 15) - (11z + 2)
= (5z-11z) +(15-2)
= -6z+13
Let the side length of the square be x, then A = x^2
but diagonal (z) = sqrt(2x^2)
z^2 = 2x^2
x^2 = 1/2 z^2
Thus, A = 1/2 z^2
dA/dz = 1/2 (2z) = z
The rate of change is z.
When z = 4, the rate is 4.