Ik this is late, but people who are looking for the answer can see this.
Answer:
an =1/3*6^n-1
Step-by-step explanation:
You should plug in 2 for n in each equation, which, the correct one should give you 2. Then, to make sure, you plug in 3 in the equations that gave you 2.
Example:
an = 1/3 * 6 ^n-1
Plug in 2.
an = 1/3 * 6 ^2-1
an = 1/3 * 6 ^1
1/3 * 6 = 2
Step 2.
an = 1/3 * 6 ^3-1
an = 1/3 * 6 ^2
1/3 * 36 = 12
Hope this helps.
You can not solve for a as all of the numbers are unknown
The general formula for the lateral surface area of a regular pyramid is:

Where:
p=perimeter of a base
l=slant height
a.
a=3ft
l=4ft
p=5*a=5*3=15ft

b.
a=2.5ft
l=4ft
p=6*a=6*2.5=15ft

c.
a=1.9ft
l=4ft
p=8*a=8*1.9=15.2ft

d.
Based on a lateral surface area the blue umbrella is best choice. But, the best umbrella overall is the one with the greatest base area. General formula for regular polygon is:

For pentagon:
A=15.48ft^2
For hexagon:
A=16.24ft^2
For octagon:
A=17.43ft^2
Blue umbrella is still best choice.
It should be 17, 26, 35, 44, 53
Answer:
(a)First Row, First Column =1
(b)First Row, second Column =0
(c)Second Row, First Column =0
(d)Second Row, second Column =1
Step-by-step explanation:
Given matrix 
The Inverse of a 2X2 matrix

can be found using the following:

Therefore:

Next, we find the product 

Therefore:
(a)First Row, First Column =1
(b)First Row, second Column =0
(c)Second Row, First Column =0
(d)Second Row, second Column =1
NOTE: The multiplication of a matrix and its inverse always gives the identity matrix as seen above,