
(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.

Domain restrictions are what x values make the denominator zero.
a² + 5a - 36 = (a + 9)(a - 4)
a ≠ -9 ; a ≠ 4
Answer:
Option D
Step-by-step explanation:
Whenever we take a square root of a number the ± sign is with it like here in the question

And then x = ±4.47 which means x has two values one is +4.47 and the other is -4.47 so Option D is our answer.
Answer:
A
Step-by-step explanation:
Because 45 + 2x = 180 divide it by 2 gives 4
7 = 2n - 2
n= a number so twice a number is 2n and 7 is 2 less than twice this number.