Answer:

Step-by-step explanation:
Factor out comon Term -1

Factor 

Use the rational root theorem

The dividers of
: 1, 5, The dividers of
: 1
Therefore, check the following rational numbers: ±
is a root of the expression, so factor out 




A.) P(t) = P0exp(kt)
P(20/60) = 40 exp(20k/60)
80 = 40 exp(k/3)
exp(k/3) = 80/40 = 2
k/3 = ln(2)
k = 3ln(2)
b.) P(8) = 40(2)^24 = 40(16777216) = 671088640 cells
d.) Rate of change = exp(8k) = exp(8(3ln(2)) = exp(24ln(2)) = exp(16.6355) = 16777216 cells / hour
e.) P(t) = 40(2)^3t; t in hours
1,000,000 = 40(8)^t
25,000 = 8^t
ln(25,000) = t ln(8)
t = ln(25,000)/ln(8) = 4.87 hours
first off, let's notice that Purple's time is in minutes, whilst the rate is in miles per hour, the units of both must correspond, so, we can either change the time from minutes to hours or the rate from hours to minutes, hmmm let's change the time to hours.
so 40 minutes, we know there are 60 minutes in 1 hour, so 40 minutes will be 40/60 of an hr, or namely 2/3.
![\qquad \qquad \textit{inverse proportional variation} \\\\ \textit{\underline{y} varies inversely with \underline{x}} ~\hspace{6em} \stackrel{\textit{constant of variation}}{y=\cfrac{\stackrel{\downarrow }{k}}{x}~\hfill } \\\\ \textit{\underline{x} varies inversely with }\underline{z^5} ~\hspace{5.5em} \stackrel{\textit{constant of variation}}{x=\cfrac{\stackrel{\downarrow }{k}}{z^5}~\hfill } \\\\[-0.35em] ~\dotfill](https://tex.z-dn.net/?f=%5Cqquad%20%5Cqquad%20%5Ctextit%7Binverse%20proportional%20variation%7D%20%5C%5C%5C%5C%20%5Ctextit%7B%5Cunderline%7By%7D%20varies%20inversely%20with%20%5Cunderline%7Bx%7D%7D%20~%5Chspace%7B6em%7D%20%5Cstackrel%7B%5Ctextit%7Bconstant%20of%20variation%7D%7D%7By%3D%5Ccfrac%7B%5Cstackrel%7B%5Cdownarrow%20%7D%7Bk%7D%7D%7Bx%7D~%5Chfill%20%7D%20%5C%5C%5C%5C%20%5Ctextit%7B%5Cunderline%7Bx%7D%20varies%20inversely%20with%20%7D%5Cunderline%7Bz%5E5%7D%20~%5Chspace%7B5.5em%7D%20%5Cstackrel%7B%5Ctextit%7Bconstant%20of%20variation%7D%7D%7Bx%3D%5Ccfrac%7B%5Cstackrel%7B%5Cdownarrow%20%7D%7Bk%7D%7D%7Bz%5E5%7D~%5Chfill%20%7D%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill)

Answer:
no expression is equal to -20