The answer is E your welcome
Usually one will differentiate the function to find the minimum/maximum point, but in this case differentiating yields:

which contains multiple solution if one tries to solve for x when the differentiated form is 0.
I would, though, venture a guess that the minimum value would be (approaching) 5, since the function would be undefined in the vicinity.
If, however, the function is

Then differentiating and equating to 0 yields:

which gives:

or

We reject x=5 as it is when it ix the maximum and thus,

, for
Answer:
DK = 9
Step-by-step explanation:
In triangle AMD,
h² = p² + b²
or, h² = 6² + 4²
or, h²= 36 + 16
so, h² = 52
so, AM² = 52
Take x as reference angle,
cos²x = 16/52
Now,
In triangle, AMK,
Taking x as reference angle,
cos²x = b²/h²
cos²x = AM²/MK²
or, cos²x = 52/MK²
Now,
cos²x = 16/52 = 52/MK²
or,
16/52 = 52/MK²
or, 16MK² = 2704
or, MK² = 2704/16
or, MK² = 169
so, MK = 13
Now,
DK = MK - MD
or, DK = 13 - 4
so, DK = 9