Answer: D
Step-by-step explanation:
Answer:
Option A.

Step-by-step explanation:
see the attached figure with letters to better understand the problem
In this problem we have a triangle with a circle inscribed in it
so

step 1
Find the length side B.C

substitute the given values

step 2
Find the length side C.D
Remember that

therefore

step 3
Find the length side E.D
we know that

substitute the given values

step 4
Find the length side E.F
Remember that

therefore

step 5
Find the length side A.F
Remember that

therefore

step 6
Find the perimeter


Distribution method
(2x+6)(2x-6)
=4x^2-12x+12x-36
=4x^2-36