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Arithmetic Sequences Lesson

Arithmetic Sequences Lesson

Assessment

Presentation

Mathematics

9th - 12th Grade

Easy

CCSS
HSF.BF.A.2, HSF.LE.A.2, HSF.IF.A.3

+2

Standards-aligned

Created by

Victoria Colbert

Used 1+ times

FREE Resource

9 Slides • 24 Questions

1

Sequences

A sequence is an ordered list of numbers. Each number in a sequence is called a term. Each term an has a specific position n in the sequence.

example: 5, 10, 15, 20, 25,…an

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2

Arithmetic Sequence

An arithmetic sequence is a sequence where you add a constant number to find the next term, similar to the constant rate of change in a linear function.


In an arithmetic sequence we only add to find the next number (term). This number can be positive or negative.

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3

Term

In a sequence each number is called a term.


The dots at the end mean the sequence continues forever.


a1 is the first term

a2 is the second term

a3 is the third term and so on...

an is the nth term (we will find the equation for the nth term in the next lesson)

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4

Common Difference

The number you add/subtract to find the next term in a sequence is called the common difference.


Subtract two terms to find the common difference. d is used to define the common difference

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5

Ready to try some examples?

Remember in an arithmetic sequence, each number is found by adding a common difference, which can be positive or negative.

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6

Multiple Choice

Identify the common difference.

10, 20, 30, 40, ...

1

5

2

10

3

15

4

20

7

Multiple Choice

The next two terms of the sequence 12,17,22,27 are

1

28 and 33

2

29 and 34

3

32 and 37

4

30 and 35

8

Multiple Choice

The next two terms of the sequence 4,7,10,13 are
1
16 and 19
2
15 and 19
3
16 and 18
4
15 and 18

9

Multiple Choice

Find the common difference: 29, 21, 13, 5, ...


Remember, the common difference is the difference between the numbers.

1

d = -10

2

d = -9

3

d = -8

4

d = -7

10

Multiple Choice

Is the sequence arithmetic: 37, 31, 25, 19, ...
1
Yes
2
No

11

Multiple Select

Which sequences are arithmetic?

(hint: select 2)

1

2, 4, 6, 8, 10 ...

2

5, 10, 20, 40, 80, 100 ...

3

1, 3, 7, 9, 15, 20 ...

4

4, 8, 12, 16, 20, 24 ...

12

Fill in the Blanks

13

Multiple Choice

If the first term of an arithmetic sequence is 5 and the common difference is 6, what are the first five terms?

1

5, 11, 17, 23, 29

2

6, 11, 16, 21, 26

3

5, 10, 15, 20, 25

4

5, 11, 15, 20, 26

14

Multiple Choice

Which sequence has a common difference of 4?

1

4, 6, 8, 10, 12...

2

1, 5, 9, 13, 17....

3

4, 4, 4, 4, 4...

4

4, 14, 24, 34, 44...

15

Fill in the Blanks

16

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17

Multiple Choice

We will start with the explicit formula. Given the following sequence, state the first term and common difference.

Example 1:          4, 7, 10, 13, 16, …

1

a1 = 3,   d = 4a_1\ =\ 3,\ \ \ d\ =\ 4    

2

  a1 = 16,   d = 3a_1\ =\ 16,\ \ \ d\ =\ 3  

3

  a1 = 4,   d = 3a_1\ =\ 4,\ \ \ d\ =\ 3  

4

  a1 = 16,   d = 13a_1\ =\ 16,\ \ \ d\ =\ 13  

18

Multiple Choice

Now, write the explicit formula for the given sequence.

Example 1:          4, 7, 10, 13, 16, …

1

an = 4 + (n  1)(3)a_n\ =\ 4\ +\ \left(n\ -\ 1\right)\left(3\right)  

2

an = 3 + (n  1)(4)a_n\ =\ 3\ +\ \left(n\ -\ 1\right)\left(4\right)  

3

an = 7 + (n  1)(3)a_n\ =\ 7\ +\ \left(n\ -\ 1\right)\left(3\right)  

4

an = 16 + (n  1)(4)a_n\ =\ 16\ +\ \left(n\ -\ 1\right)\left(4\right)  

19

Multiple Choice

Write an explicit rule to model the following sequence:

Example 2: 21, 19, 17, 15, …

1

an = 21 +(n  1)(2)a_n\ =\ 21\ +\left(n\ -\ 1\right)\left(2\right)  

2

an = 21 +(n  1)(2)a_n\ =\ -21\ +\left(n\ -\ 1\right)\left(2\right)  

3

an = 21 +(n  1)(2)a_n\ =\ -21\ +\left(n\ -\ 1\right)\left(-2\right)  

4

an = 21 +(n  1)(2)a_n\ =\ 21\ +\left(n\ -\ 1\right)\left(-2\right)  

20

Multiple Choice

Write and explicit rule to model the following sequence:

Example 3:        -12, -7, -2, …

1

an = 5 + (n 1)(12)a_n\ =\ 5\ +\ \left(n\ -1\right)\left(-12\right)  

2

an = 12 + (n 1)(5)a_n\ =\ -12\ +\ \left(n\ -1\right)\left(5\right)  

3

an = 5 + (n 1)(12)a_n\ =\ -5\ +\ \left(n\ -1\right)\left(12\right)  

4

an = 12 + (n 1)(5)a_n\ =\ 12\ +\ \left(n\ -1\right)\left(-5\right)  

21

Multiple Choice

Find the 26th term in the arithmetic sequence: 20, 26, 32, 38, ...
1
182
2
176
3
170
4
-118

22

Fill in the Blanks

23

Multiple Choice

Now, let's go backwards!!! Given the explicit formula, list the first five terms in order.

an = 3 + (n  1)(2)a_n\ =\ 3\ +\ \left(n\ -\ 1\right)\left(2\right)  

1

2, 5, 8, 11, 14, ...

2

3, 1, -1, -3, -5, ...

3

3, 6, 9, 12, 15, ...

4

3, 5, 7, 9, 11, ...

24

Now, let's simplify the explicit formula even further

  an = 4 + (n - 1)(-2) **What do you see that we can do to this equation?

Some text here about the topic of discussion

25

Now, our equation is an = -2n + 6

  an = -2n + 6 **How does this resemble linear equation in slope- intercept form?

y = mx + b​ Slope-Intercept Form

Some text here about the topic of discussion

26

Arithmetic Sequences Model Linear Functions!!!

  an = -2n + 6 **The common difference is the same as the slope!

y = mx + b​ **The y-intercept is the difference of the first term

and the common difference... or b = a1 - d

Some text here about the topic of discussion

27

Multiple Choice

Create the explicit formula for the sequence:
2, 8, 14, ...
(Hint:  Write your formula and then simplify it.)
1

an = 6n + 2

2

an = 6n - 6

3

an = 6n - 4

4

an = -6n + 4

28

Multiple Choice

Find the 25th term of the sequence if a1 = 5 and d = 0.5
1
18
2
17
3
15
4
14

29

Multiple Choice

Find the explicit formula:
-3, -33, -63, -93, ...
1
an = -3 - 30(n -1)
2
an = -3 + 30(n -1)
3
an = -30 - 3(n -1)
4
an = -30 + 3(n -1)

30

Multiple Choice

Find the explicit formula:
-23, -16, -9, -2, ...
1
an = -23 + 7(n -1)
2
an = -23 - 7(n -1)
3
an = 7 - 23(n -1)
4
an = 7 + 23(n -1)

31

Multiple Choice

Find the term named in the problem
14, 22, 30, 38, ... a22
1
190
2
182
3
169
4
127

32

Multiple Choice

Find the term named in the problem
14, 214, 414, 614, ... a30
1
5724
2
5814
3
5784
4
5614

33

Multiple Choice

Given the arithmetic sequence
a= 14 + (n-1)9 
which equation is equivalent
1
a= 9n-5
2
a= 9n+5
3
a= 5n +9
4
a= 9 + 14(n-1) 

Sequences

A sequence is an ordered list of numbers. Each number in a sequence is called a term. Each term an has a specific position n in the sequence.

example: 5, 10, 15, 20, 25,…an

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