The derivative of
in the direction of a vector
is

With
, we get

and
,

Then

Answer:
2x+12
Step-by-step explanation:
We have a square patio, then each side of the patio has the same lengt. As we know the perimeter of a square is the sum of all sides. Then to know the length of the patio we just need to divide by 4 the perimeter.

Then each side of the square patio has a length of 2x+12
<span> -x2 - 2x - 4 which is B</span>