A sequence is a
function whose domain
is the finite set {1,23,
…, n} or the infinite
set {1,2 ,3,…}.
2 3 4 5
Example:
n 1
a(n) 4 5 6 7
2 3 4…
Example:
n 1
a(n) 2 4 6 8…
Activity: Termafter Term
Find the first five terms
of the sequence given
the nth term.
1. 𝑎𝑛= 𝑛+ 4
2. 𝑎𝑛= 2𝑛− 1
3. 𝑎𝑛= 12 − 3𝑛
4. 𝑎𝑛= 3𝑛
5. 𝑎𝑛= (−2)𝑛
Activity: Getting to know
you!
What is the nth term for each
sequence below?
1. 3, 5, 7, 9, 11, …
2. 3, 4, 5, 6, 7, …
3. 6, 8, 10, 12, 15, …
4. 15, 17, 19, 21, 23, ...
5. 11, 14, 17, 20, 23,
...
ARITHMETIC
SEQUENCE
An arithmetic
sequence is a sequence
where every term after
the first is obtained by
adding a constant called
the common difference.
The sequences
1,4,7,10,... and 15, 11, 7,
3,... are examples of
arithmetic sequences since
each one has a common
difference of 3 and -4.
Arithmetic Rule
an= a1+(n - 1)d
•a1 is the first term in the sequence
•n is the number of the term you are
trying to determine
•d is the common difference
•an is the value of the term that are
looking for
Try this…
Use the arithmetic formula to
determine the 100th term of
the following sequence:
75, 25, -25, -75, -125,…
an = a1+ (n - 1)d
= 75 + (100 – 1)(-50)
= -4875
a1 = 75
n = 100
d = -50
Try this…
Use the arithmetic formula to
determine the 10th term of
the following sequence:
5, 12, 19, 26,…
an = a1+ (n - 1)d
= 5 + (10 –
1)(7)
= 68
a1 = 5
n =
10
d = 7
What is missing?
1. 3, 12, 21, 30 , 39 ,
48
2. 8, 3, -2, -7 ,-12
3. 5, 12, 19 ,
What is missing?
4. -4 , 0 , 4 , 8 , 12 , 16
5. -1, 7 , 15 , 23, 31,
39
6. 13, 7 , 1 ,_-5_,-11.-
Insert three terms
between 2 and 34 of
an arithmetic
sequence.
ARITHMETIC MEANS
The terms between
any two consecutive
terms of an arithmetic
sequence.
Insert4 arithmetic
means between 5
and 25.
Solution:
Since we are required
to insert 4terms, then
there will be 6 terms in
all.
Let 𝑎1 = 5and 𝑎6 = 25
5, 𝑎2,𝑎3,𝑎4,𝑎5,25
5, 𝑎2,𝑎3,𝑎4,𝑎5,25
Let 𝑎6 = 𝑎1+
25 = 5 +
6 − 1 𝑑
5 𝑑
20 − 5 = 5𝑑
4 = 𝑑
5, 𝑎2,𝑎3,𝑎4,𝑎5,25
𝑎2 = 𝑎1+ (1)(𝑑) n = 2
(2 – 1) =
1
𝑎2 = 5 + 1 4 = 9
𝑎3 = 5 +
(2)(4)=13
𝑎4 = 5 + 3
𝑎5 = 5 +
4 = 17
4 4 = 21
Insert 2 arithmetic
means between ½
and 2.
ARITHMETIC SUM
Sum of the terms in an
arithmetic sequence.
What is
1 + 2 + 3 + …+ 50 + 51
+… + 98 + 99 +100?
Formula:
𝑛
𝑆𝑛 =
2
(𝑎1 + 𝑎𝑛)
𝑛
𝑆𝑛 =
2
[2𝑎1 + 𝑛− 1 𝑑]
𝑎𝑛 = 𝑎1 + 𝑛− 1 𝑑
Example:
Find the sum of the first
10 terms of the
arithmetic sequence 5,
9, 13, 17,…
Using the formula:
𝑛
𝑆𝑛 =
2
[2𝑎1 + 𝑛− 1 𝑑
]
10
𝑆10 =
2
[2(5) + 10 − 1 4]
d = 9 -
5
𝑆10 = 5 10 + 9 4 = 5 46 = 𝟐𝟑𝟎
Example:
Find the sum of the first
20 terms of the
arithmetic sequence -2,
-5, -8, -11, …
-610
Activity:
How well do
you know me?
Which of the following
sequences is an
arithmetic sequence?
Why?
1. 3, 7, 11, 15, 19
2. 4, 16, 64, 256
3. 48, 24, 12, 6, 3, …
4. 1, 4, 9, 16, 25, 36
5. 1, ½ , 0, - ½
6. – 2, 4, - 8, 16, …
7. 1, 0, -1, -2, -3
8. ½ , 1/3, ¼ , 1/5
9. 3x, x, x/3, x/9
10. 9.5, 7.5, 5.5, 3.5
Find the 25th term of
the arithmetic
sequence 3, 7, 11,
15, 19,…
The second term of the
arithmetic sequence is
24 and the fifth term is
3. Find the first term
and the common
difference
Give the arithmetic
sequence of 5
terms if the first
term is 8 and the
last term is 100.
What must be the
value of k so that
5k – 3, k +2, and
3k – 11 will form an
arithmetic sequence?

math 10 aug. 6, 2023.pptx