Solve It! A wooden post-and-rail fence with two rails is made as shown.

Find the number of pieces of wood needed to build a 4-section fence, a 5-section fence, and a 6-section fence. Not all items will be used.
26 pieces
20 pieces
16 pieces
25 pieces
19 pieces
27 pieces
13 pieces
24 pieces
4-section fence
5-section fence
6-section fence

Take Note: Define sequence.
Take Note: Define term of a sequence.

Problem 1 Got It?

Problem 1 Got It?

Problem 1 Got It?

Problem 1 Got It?

Take Note: Define arithmetic sequence.
Take Note: Define common difference (of an arithmetic sequence).
Take Note: Provide an example of an arithmetic sequence with a common difference of 3 that includes 5 terms.

Problem 2 Got It?

Problem 2 Got It?

Problem 2 Got It?

Problem 2 Got It?
TAKE NOTE Key Concept
Recursive Formula For an Arithmetic Sequence
The nth term of an arithmetic sequence with first term A(1) and common difference d is given by

Take Note: Define recursive formula.
Problem 3 Got It? Write a recursive formula for the arithmetic sequence.
Problem 3 Got It? What is the 9th term of the arithmetic sequence?
Problem 3 Got It? Write a recursive formula for the arithmetic sequence.
Problem 3 Got It? What is the 9th term of the arithmetic sequence?
Problem 3 Got It? Write a recursive formula for the arithmetic sequence.
Problem 3 Got It? What is the 9th term of the arithmetic sequence?
Problem 3 Got It? Write a recursive formula for the arithmetic sequence.
Problem 3 Got It? What is the 9th term of the arithmetic sequence?
Problem 3 Got It? Reasoning: Is a recursive formula a useful way to find a value of an arithmetic sequence?
HINT: What if you want to find the 91st term in an arithmetic sequence?

Take Note: Define explicit formula.

Problem 4 Got It?

Problem 4 Got It?

Problem 5 Got It?

Problem 5 Got It?

Problem 6 Got It?

Problem 6 Got It?

Take Note: Summarize the mathematical content of this lesson. What topics, ideas, and vocabulary were introduced?
Take Note: In a recursive formula, why is it important to define the first term of the sequence?
Take Note: In a recursive formula, what does n represent?
Take Note: In a recursive formula, what does A(n) represent?
Take Note: In a recursive formula, what does A(1) represent?
Take Note: In a recursive formula, what does d represent?
Take Note: In an explicit formula, what does n represent?
Take Note: In an explicit formula, what does A(n) represent?
Take Note: In an explicit formula, what does A(1) represent?
Take Note: In an explicit formula, what does d represent?