Objective: 1. After completing activity 1, mod. 10 2. With 90% accuracy 3. -Identify sequences as arithmetic, geometric, or neither -Write recursive formulas for arithmetic and geometric sequences -Write explicit formulas for arithmetic and geometric sequences -Determine the number of terms in a finite arithmetic or geometric sequence
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Objective: 1. After completing activity 1, mod. 10 2. With 90% accuracy 3. -Identify sequences as arithmetic, geometric, or neither -Write recursive formulas.
Simple test to check if a pattern is an arithmetic sequence: Check that the difference between consecutive terms is constant. For example, in the sequence: 1,2,3,4,5,6,… the constant is one because 6-5=5-4=4-3=3-2=2-1=1 In other words, since the difference is constantly 1, then it is an arithmetic sequence
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Objective: 1. After completing activity 1, mod. 102. With 90% accuracy3. -Identify sequences as arithmetic, geometric,
or neither -Write recursive formulas for arithmetic and
geometric sequences -Write explicit formulas for arithmetic and
geometric sequences -Determine the number of terms in a finite
arithmetic or geometric sequence
Arithmetic Sequence:An arithmetic (linear) sequence is a
sequence of numbers in which each new term ( )is calculated by adding a constant vale(d) to the previous term.
For example: 1,2,3,4,5,6,…The value of d is 1. Find the constant value that is added to
get the following sequences & write out the next 3 terms.
1. 2,6,10,14,18,22,…
na
Simple test to check if a pattern is an arithmetic sequence: Check that the difference
between consecutive terms is constant.
For example, in the sequence: 1,2,3,4,5,6,… the constant is one because
6-5=5-4=4-3=3-2=2-1=1 In other words, since the difference
is constantly 1, then it is an arithmetic sequence
Find the constant value that is added to get the following sequences & write out the next 3 terms
2,6,10,14,18,22,… (you did this
one already) -5,-3,-1,1,3,… 1,4,7,10,13,16,… -1,10,21,32,43,54,… 3,0,3,-6,-9,-12,…
The recursive formula for an arithmetic sequence
constant termprevious
termnew
1
1
daa
daa
n
n
nn
For example, the recursive formula for the arithmetic sequence 1,2,3,4,5,6… is
11 nn aa
Write the recursive formula for each sequence: 2,6,10,14,18,22,… -5,-3,-1,1,3,… 1,4,7,10,13,16,… -1,10,21,32,43,54,… 3,0,3,-6,-9,-12,…
Answers:
311324
1
1
1
1
1
nn
nn
nn
nn
nn
aaaaaaaaaa
Explicit formula The explicit formula for a
sequence defines any term based on its term number (n):
number termcostant
pattern in first term termnew
)1(
1
1
ndaa
ndaa
n
n
Write the explicit formula for each sequence 2,6,10,14,18,22,… -5,-3,-1,1,3,… 1,4,7,10,13,16,… -1,10,21,32,43,54,… 3,0,3,-6,-9,-12,…
Answers:
)1(33)1(111
)1(31)1(25
)1(42
nana
nanana
n
n
n
n
n
Use your explicit formulas to answer the questions: (show your work)
1. What is the third term in the pattern:
2,6,10,14,18,22,…
2.What is the 20th term?
3.What is the 35th term?
Answers:
1082
)2(42)13(42)1(42
sequence in the term3rd The
n
n
n
n
n
aaaa
na
782
)19(42)120(42
)1(42sequence in the 20th term
n
n
n
n
n
aaaa
na
1381362
)34(42)135(42
)1(42 sequence in the 35th term
n
n
n
n
n
aaaa
na
Geometric Sequence:A geometric sequence- every
term after the first is formed by multiplying the preceding term by a constant value called the common ratio (or r)
For example: 2,10,50,250,1250 ◦The value of r is 5 because :
on... so and 51050 5
50250 5
2501250
Simple test to check if a sequence is a geometric sequence:
r or 11
2
2
3 n
n
aar
aa
aa
When you divide a term by a previous term you must arrive at equal common ratios.
Determine the common factor for the following geometric sequence: 5,10,20,40,80,…
7,28,112,448,…2,6,18,54,…
,...81,
41,
21
Answer:2½43
The recursive formula for a geometric sequence
ratiocommon r termprevious termnew
1
1
n
n
nn
aa
raa
Write the recursive formula for each geometric sequence :•5,10,20,40,80,…•
•7,28,112,448,…•2,6,18,54,…
,...81,
41,
21
Write the recursive formula for each geometric sequence
• 5,10,20,40,80,…•
• 7,28,112,448,…• 2,6,18,54,…
,...81,
41,
21
Answers:
1
1
1
1
3
421
2
nn
nn
nn
nn
aa
aa
aa
aa
The explicit formula for a geometric series is:
number termnratiocommon first term termnew
1
11
raa
raa
n
nn
Write the explicit formula for each geometric sequence :•5,10,20,40,80,…•
•7,28,112,448,…•2,6,18,54,…
,...81,
41,
21
Answers:
1n
1n
1
n
1n
32a
47a21
21a
25a
n
n
n
n
Is the following sequence arithmetic or geometric?: -3,30,-300,3000,….
Write a recursive & explicit formula for it.
Use the explicit formula to find the 8th term.
Answer: Geometric
1
1
)10(3
10
n
n
nn
a
aa
Warm-up 3/8/10State whether the sequence is
arithmetic, geometric, or neither. Use your notes.
1
2
)3(4
)2(
200163
nn
n
n
a
na
na
Answers: ArithmeticNeitherGeometric
Warm-Up 3/9/10 (head your paper) Consider the following arithmetic
sequences: 0, 6, 12, 18,…1201, 9, 17, 25,…9715, 12, 9, 6,…-21What is the common difference for
each?How many terms are in the
sequence?
Class work:Remember to head your
notebook with page # & today’s date.
Old green Alg. II Book page 476 #1-9 under Exercises & Applications also do #13 & 14 . Be Ready for a Quiz on it!
Your regular book: Page 277 Assignment #1.1, 1.3, 1.4, 1.9
Class work: 3/9/10 Old green Alg. II book page 479
#35-37Read the problem carefully
Your regular book Page 277 Assignment #1.5 a-c
Homework: Page 274-275 a-f.
Page 277 Warm-up #1-2
Homework Review, Check your work: Page 274 Discussion a. 1. arithmetic 2. geometric 3. neither 4. geometric5. neither 6. Fibonacci
Discussion b.
31 ;162a .)2
6 ;7a .)1
11
1n1
nn
n
aa
aa
Objective: 1.After completing activity 2, mod. 102. With 90% accuracy3.-Identify sequences as arithmetic,
geometric, or neither Write explicit formulas for arithmetic
and geometric sequences Determine the number of terms in a
finite arithmetic sequenceWrite formulas for finite arithmetic
series
Activity 2 NotesFinite Series- the sum ( )of the
terms of a finite sequence. ◦For example: a finite series with n
terms is: ◦
Arithmetic Series: the sum of the terms of an arithmetic sequence. For example:
nS
nn aaaaS ...321
561412108642,12,142,4,6,8,10 :Series ArithmeticnS
Find the sum of the first 100 natural numbers:
5050. is numbers natural 100first theof sum The
50502
)101(100S
2)by equation of sidesboth (divide )101(1002S :Therefore 100 there?are 101 of setsmany How