Remember to incorporate Bimdas, into you calculation and ensure where the addition and subtraction occur you work from left to right.
You will need to add all the dimensions together, also know as perimeter
Answer: I gave the evaluate answer and the differentiate w.r.t x answer. Sorry for caps.
Step-by-step explanation: EVALUATE x4n−3
DIFFERENTIATE W.R.T. X (4n−3)x4(n−1)