Y2CH3 Sequences and series Flashcards
Arithmetic Un formula
Un = a + (n-1)d
Arithmetic sum forumla
sn = n/2 (2a + (n-1)d)
What do geometric sequences have between consecutive terms
Common ratio
Geometric term formula
Un = ar^n-1
What is r
The common ratio
a/b = b/c
Geometric series formula
Sn = a(1-r^n) / 1-r
What is a divergent series
When terms of a series is getting larger as n tend to infinitiy
What is a convergent series
When the terms are getting smaller as Sn gets closer to finite
Convergent geometric series is given by?
S = a / 1 - r
When can you use convergent series formula
When r < 1
What is the sigma notation used for?
The sum of
What is a recurrence relation
When you plug in previous values of the sequence into the formula
How do you know if a sequence is decreasing or increasing
When Un+1 >/< Un
What is a periodic sequence
A sequence that rotates in a cycle
