Sequences - Brookwood High School

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May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Sequences

EOCT: May 10-11

Vocabulary

• Sequence: an ordered list of numbers

– Ex. -2, -1, 0, 1, 2, 3

• Term: each number in a sequence

– Ex. a

1

, a

2

, a

3

, a

4

, a

5

, a

6

• Infinite Sequence: sequence that continues infinitely

– Ex: 2, 4, 6, 8, …

• Finite Sequence: sequence that ends

– Ex: 2, 4, 6

• Explicit Formula: defines the nth term of a sequence .

Example 1:

A) Write the first six terms of the sequence defined by a n

= 4n + 5

B) Write the first six terms of the sequence defined by a n

= 2n 2 – 1

Vocabulary

• Recursive Formula:

– Uses one or more previous terms to generate the next term. a n-1

Example 2:

A) Write the first six terms of the sequence where a

1

= -2 and a n

= 2a n-1

– 1

B) Write the first six terms of the sequence where a

1

= 4 and a n

= 3a n-1

+ 5

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Arithmetic Sequences

EOCT: May 10-11

Vocabulary

• Arithmetic Sequence:

– A sequence generated by adding “d” a constant number to pervious term to obtain the next term.

– This number is called the common difference .

• What is d? a

2

– 3, 7, 11, 15, …

– a

1

– 8, 2, -4, -10, … d = 4 d = -6

Formula for the n th term

Common difference

First term in the sequence a n

= a

1

+ (n – 1)d

What term you are looking for

What term you are looking for

Example 1:

A) Find the 10 th term of a

1 a n

= a n-1

+ 6

= 7 and d

B) Find the 7 th term of a

1 a n

= a n-1

- 3

= 2.5 and

Example 2:

A) Find the 10 th term of the arithmetic sequence where a

3

= -5 and a

6

= 16

B) Find the 15 th term of the arithmetic sequence where a

5

= 7 and a

10

= 22

C) Find the 12 th term of the arithmetic sequence where a

3

= 8 and a

7

= 20

Vocabulary

• Arithmetic Means:

– Terms in between 2 nonconsecutive terms

– Ex. 5, 11, 17, 23, 29  11, 17, 23 are the arithmetic means between 5 & 29

Example 3:

A) Find the 4 arithmetic means between

10 & -30

B) Find the 5 arithmetic means between

6 & 60

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Geometric Sequences

EOCT: May 10-11

Vocabulary

• Geometric Sequence:

– A sequence generated by multiplying a constant ratio to the previous term to obtain the next term.

– This number is called the common ratio .

• What is r?

a

2 a

1

 r

– 2, 4, 8, 16, …

– 27, 9, 3, 1, … r = 2 r = 1/3

Formula for the n th term

First term in the sequence a n

= a

1 r n-1

What term you are looking for

Common Ratio

What term you are looking for

Example 1

• Find the 5 th term of a

1

= 8 and a n

= 3a n-1

• Find the 7 th term of a

1

= 5 and a n

= 2a n-1

Example 2:

A) Find a

10 of the geometric sequence

12, 18, 27, 40.5, …

B) Find a

7 a

1 of the geometric sequence where

= 6 and r = 4

Homework

P.140 #1-16

P.145 #1-17

***Keep reviewing for your EOCT***

(May 10-11)

Warm up

1. Find the 8 th term of the sequence defined by a

1

= –4 and a n

= a n-1

+ 2

2. Find the 12 th term of the arithmetic sequence in which a

4

= 2 and a

7

= 6

3. Find the four arithmetic means between 6 and 26.

4. Find the 5 th term on the sequence defined by a

1

= 2 and a n

= 2a n-1

.

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Series

( M2 )

EOCT: May 10-11

Series

• Series: the sum of a sequence

– Sequence: 1, 2, 3, 4

– Series: 1 + 2 + 3 + 4

Summation Notation - __________________

EX. (for the above series)

• Summation Notation: n

4

1

2 n

1

n

4

1

2 n

1

= _______ + _______ + _______ + _______

= ____ + _____ + _____ + _____ = _____

Summation Properties

• For sequences a k and b k and positive integer n :

1) k n 

1 ca k

 c a k k n 

1

2) k n 

1

 a k

 b k

  k n  

1 a k

 n

1 k b k

Summation Formulas

• For all positive integers n :

Constant k n 

1 c

 nc k n 

1 k n 

1 k

2 

Quadratic

(

1)(2 n

1)

6 k

Linear

(

1)

2

Example 1:

A) Evaluate k

6

1

2 k

B) Evaluate 4 k

6

1 k

Extra Example:

• Evaluate m

5 

1

(

Not in packet

)

(2 m

2 

3 m

2)

Homework:

P.135 #18-24

*work on Benchmark Practice WS*

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Arithmetic Series

( M2 )

EOCT: May 10-11

Sequences and Series Test: May 18

Vocabulary

• An Arithmetic Series is the sum of an arithmetic sequence.

Formula for arithmetic series

S n

= n

 a a n

2 

Example 1:

A.

Find the series 1, 3, 5, 7, 9, 11

B. Find the series 8, 13, 18, 23, 28, 33, 38

Example 2:

A) Given 3 + 12 + 21 + 30 + …, find S

25

B) Given 16, 12, 8, 4, …, find S

11

A) Evaluate k

12 

1

Example 3:

B) Evaluate k

21 

1

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Geometric Series

( M2 )

EOCT: May 10-11

Sequences and Series Test: May 18

Vocabulary

• An Geometric Series is the sum of an geometric sequence.

Formula for geometric series

S n

= a

1



1

1

 r n r 



Example 1:

• Given the series

3 + 4.5 + 6.75 + 10.125 + …find S

10 to the nearest tenth.

n

• Evaluate

Example 2: k

7 

1

4( 5) k

1 r a

1

• Evaluate k

6 

1

2

Homework

• P. 141 #16-27

• P. 145 #18-23

• Study/Review for EOCT!

( Sequences and Series ARE ON the EOCT )

May 10-13 and May 17-20:

School starts at 7:15 for

EOCT testing!

Infinite Geometric Series

( M2 )

Sequences and Series Test: May 18

Finals:

1 st Period – May 21

2 nd Period – May 24

6 th Period – May 26

Vocabulary

• An Infinite Geometric Series is a geometric series with infinite terms.

Formula for infinite geometric series

S =

( 1 a

1

 r )

If

 r

<1 then the _______ can be found

If

 r

>1 then the _______ cannot be found

Example 1:

A) Find the sum of the infinite geometric series 3 + 1.2 + 0.48 + 0.192 + …

B) Find the sum of the infinite geometric series 8 + 9.6 + 11.52 + 13.824 + …

Example 2:

• Find the sum of the infinite geometric series below: k

1

1

3 k

1

Example 3:

NOT IN PACKET

A. Write 0.2 as a fraction in simplest form.

B. Write 0.04 as a fraction in simplest form.

Homework

• P. 147 #32 – 45 (M2 – Purple )

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