Question

Write the equation that represents the relationship between n the number of triangles and p the perimeter of the figures formed.

Answer 1

1 triangle; Perimeter = 6+5+6 = 17
2 triangles; Perimeter = 6+5+6+5 = 22
3 triangles; Perimeter = 6+5+6+5+5 = 27

As you can see the perimeter is an arithmetic sequence with first number 17 and common difference 5.
What is the nth term of such an arithmetic sequence?