Transcript Slideshow

PRE228
UNKNOWN VALUES in ARITHMETIC SEQUENCES
ARITHMETIC SEQUENCE: a sequence of numbers where the
same term is added (or subtracted) from one term to the next.
Find the unknown number in the arithmetic sequence:
For example: –3, –1, 1,_3_, 5, 7, 9, …
7 – 5 = 2 and 9 – 7 = 2
CD = +2
1. Find the common difference.
1+2=3
2. Apply the common difference
to the missing term.
PRE228
UNKNOWN VALUES in ARITHMETIC SEQUENCES
How do you find the 21st term in a sequence?
an = a1 + (n – 1)d
a1: first term in the sequence
n: number of term you want to find (27th, 12th, etc.)
d: common difference
Find the 21st term.
Given sequence: (–3, –1, 1, 3, 5, 7, 9, …)
PRE228
UNKNOWN VALUES in ARITHMETIC SEQUENCES
How do you find the 21st term in a sequence?
an = a1 + (n – 1)d
a1: first term in the sequence
n: number of term you want to find (27th, 12th, etc.)
d: common difference
Given sequence: (–3, –1, 1, 3, 5, 7, 9, …)
a21 = –3 + (21 – 1)2
a21 = –3 + (20)2
a21 = –3 + 40
a21 = 37
PRE228
UNKNOWN VALUES in ARITHMETIC SEQUENCES
an = a1 + (n – 1)d
Find a7 (the 7th term) in a sequence where the first term is 12
and the common difference is –4.
a7 = 12 + (7 – 1)–4
a7 = 12 + (6)–4
a7 = 12 + –24
a7 = –12