Answer:
25
Step-by-step explanation:
1. Use the FOIL method (x+9)(x+9)
First, outer, inner, last

Add your like terms

2. When you add or subtract polynomials you add or subtract the like terms and then put them in order from largest to smallest exponents.
3.

4. Since it is the perimeter, we add the 3 together.

Add the like terms together:

Put them in order of exponents

Hope this helps
Answer is 91.56 You add all the numbers up and divide by 9(There are 9 numbers in the sequence).