You can reduce the percentages to fractions:


So, we have



(a)
![f'(x) = \frac{d}{dx}[\frac{lnx}{x}]](https://tex.z-dn.net/?f=f%27%28x%29%20%3D%20%5Cfrac%7Bd%7D%7Bdx%7D%5B%5Cfrac%7Blnx%7D%7Bx%7D%5D)
Using the quotient rule:


For maximum, f'(x) = 0;


(b) <em>Deduce:
</em>

<em>
Soln:</em> Since x = e is the greatest value, then f(e) ≥ f(x) > f(0)


, since ln(e) is simply equal to 1
Now, since x > 0, then we don't have to worry about flipping the signs when multiplying by x.



Taking the exponential to both sides will cancel with the natural logarithmic function in the right hand side to produce:


, as required.
The perimeter of a square is the sum of its sides and they
are all equal, so to obtain the length of each of them we divide the perimeter
of the first fence between 4:
P1= 64 feet/4 sides
P1= 16 feet
Then, the length of each side of the second fence will
increase 2 feet at each end, as shown in the figure. We have then that the
perimeter of the second fence is:
P2 = 20 feet x 4 sides
P2 = 80 feet
The sum of the perimeters of both fences is:
PT = P1 + P2
PT = 64 feet + 80 feet
PT = 144 feet
Total cost = 1.17 $ x 144 feet
Total cost = 168.48 $
The total cost of the fences was $ 168.48
Answer:
11
Step-by-step explanation:
2.2x 5 = 11