Learning Target #2
Recognize an arithmetic sequence and partial sum while formulating and evaluating
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Arithmetic Sequence
­sequence whose consecutive terms have a common difference
ex: 4, 7, 10, 13, 16, .....
the letter "d" = common difference
ex: Find d.
#1: a n = 4n + 3
#2: a
n = 7 ­ 5n
2
­the n
th
term of an arithmetic sequence has the form
a n = dn + c
where d = difference, c = a
1 ­ d
a n = dn + c
What does this graph remind you of?
a2
a1
c
3
th
ex: Find a formula for the n
term of the arithmetic sequence whose common difference is 3 and whose first term is 2
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Partial Sums
­sum of a finite arithmetic sequence with n terms:
Sn = n (a 1 + a n)
2
ex: Find the sum:
a.) 4 + 8 + 12 + 16 + 20 + 24 + 28 + 32
b.) from 1 to 100
5
th
ex: Find the 150
partial sum of the arithmetic sequence
5, 16, 27, 38, 49
6
ex: An auditorium has 20 rows of seats. There are 20 seats in the first row, 21 in the second, and so on. How many seats are in all 20 rows?
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ASSIGNMENT
p. 631 #5­7, 13­15, 25­26, 33­36, 53­55, 62, 67, 81, 82
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