In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data
A(t) = 800e^(-0.86t)
Step 02:
Rate of change
t1 = 0
A(t) = 800e^(-0.86t)
A(t) = 800e^(-0.86*0)
A(0) = 800
t2 = 5
A(t) = 800e^(-0.86t)
A(t) = 800e^(-0.86*5)
A (t) = 800e^(-4.3)
A(5) = 10.85
Step 03:
[tex]\frac{\Delta y}{\Delta x}=\frac{A(5)\text{ - A(0)}}{5-0}[/tex][tex]\frac{\Delta y}{\Delta x}=\frac{10.85-800}{5-0}=\frac{-789.15}{5}=-157.83[/tex]