Whenever you multiply by a negative number.
Hopefully that helps you a little.

(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.
D = 545.79
r = 48.3
Plug in numbers to corresponding variables
545.79 = t(48.3)
Isolate the t, divide 48.3 from both sides
(545.79)/48.3 = 48.3t/48.3
t = 545.79/48.3
t = 11.3
t = A) 11.3 h
hope this helps
Step-by-step explanation:
this two...? i think have a nice day!