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8.1 sequences comp.notebook 1 January 08, 2020 Dec 273:54 PM 81 Sequences Defining a Sequence A sequence {a n } is a list of numbers written in explicit order. e.g. If the domain is finite, then the sequence is a Ex.1 Explicit Sequence Find the first six terms and the 100 th term of the sequence {a n }, where This example is defined because it is defined in terms of n.

Transcript of 8.1 sequences comp.notebook - Amphitheater Public Schools...Each term in an arithmetic sequence can...

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8­1 Sequences

Defining a Sequence

A sequence {an} is a list of numbers written in explicit order.e.g. 

If the domain is finite, then the sequence is a

Ex.1 Explicit Sequence

Find the first six terms and the 100th term of the sequence {an}, where 

This example is defined                            because it is defined in terms of n. 

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Recursive Sequences depend on what has gone on before.

Ex. 2Find the first three terms and the sixth term for the recursive sequence defined by the following conditions:

b1=5bn=2bn­1 ­ 3  for ∀n≥2

TRYRepeat example 2 with the following conditions:

b1= ­ 4b2 = 7bn=3bn­2 + 2bn­1  for ∀n≥3

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Arithmetic Sequences

Each term in an arithmetic sequence can be obtained recursively from its preceding term by adding d.

d is the 

Recursive definition:   

Explicit definition:

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Ex. 3 Defining Arithmetic Sequences

For the arithmetic sequence {­7,­3,1,5,9,...} find:

(a) the common difference(b) a recursive rule for the nth term(c) an explicit rule for the nth term(d) the 42nd term

Ex.4 Repeat the above for the arithmetic sequence {ln2, ln6, ln18, ln54,...}

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Ex. 5 Constructing a Sequence

The third and sixth terms of an arithmetic sequence are 5 and 14, respectively. Find the common difference, first term, and an explicit rule for the nth term.

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Geometric Sequences

Each term in a geometric sequence can be obtained recursively from its preceding term by multiplying by r.

r is the   

Recursive definition:   

Explicit definition:

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Ex. 6 Defining Geometric Sequences

For the geometric sequence {4,­12,36,­108,...} find:

(a) the common ratio(b) a recursive rule for the nth term(c) an explicit rule for the nth term(d) the seventh term

Ex. 7Repeat example 6 for the geometric sequence {5­3,5­5,5­7,5­9,...}

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Ex. 8 Constructing a Sequence

The third and sixth terms of a geometric sequence are ­20 and 160, respectively. Find the common ratio, first term, and an explicit rule for the nth term.

TRY

Repeat above for a3 = 25 and a6 = 1/5

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Limit of a Sequence

Some sequences do not have a limit e.g. 

Some sequences tend towards a limit as n­>∞ e.g. 

Notation: 

L is the limit of the sequence. If L exists we say the sequence CONVERGES to L. 

Sequences that do not have limits DIVERGE.

Properties of Limits

If L and M are real numbers and                and              , then

1) Sum Rule: 

2) Difference Rule: 

3) Product Rule: 

4) Quotient Rule: 

5) Constant Multiple Rule: 

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Ex. 9 Finding the Limit of a Sequence

Determine whether the sequence converges or diverges. If it converges, find its limit.

(a)  (b) 

Ex. 10 Determining Convergence or Divergence

Determine whether the sequence with the given nth term converges or diverges. If it converges, find its limit.

(a)  n=1,2,3,...       (b) b1=4, bn=bn­1+2  ∀n≥2

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Sandwich Theorem for Sequences

If  and there is an integer N for which  

an≤bn≤cn for ∀n>N, then      .

Ex. 11

Show that the sequence                  converges, and find its limit.

Ex. 12

Determine if the sequence                converges, if it converges find its limit.

Factorials

In your groups:

Evaluate 4!

Expand n! 2 different ways.

 

What is    ? What is    ?

Which one grows faster?

What is    ? What is    ?

Which one gets smaller more quickly?