a We want to write a sequence formed by the side length of the square shown in the diagram.
Let's make a table to organize the terms.
Square n
1
2
3
4
5
6
Length, a_n
1
1
2
3
5
8
We get the sequence below.
1, 1, 2, 3, 5, 8, ...
b The name of the sequence is the Fibonacci Sequence, in which each term is the sum of the two previous terms except for the first two terms.
a_1=1, a_2=1, a_n=a_(n-2)+a_(n-1)
To find the next term, we need to find the sum of a_5 and a_6.
a_5+a_6=a_7 ⇕
5+8 = 13
The seventh term is 13.
c Since the next term is 13, we need to add a square with side length 13 to the diagram. We will place this square underneath the diagram since the spiral grows downwards.