Sequences Flashcards
When is a sequence increasing?
When every subsequent term is greater than the previous one
When is a sequence decreasing?
When Un+1 < Un
How would you describe the sequence 6,14,6,14 …
A periodic sequence of the order 2 (because there are 2 numbers that keep repeating)
What is the equation you need to know for an arithmetic sequence? (Un= ?)
Un = a + (n-1)d
What does Un stand for?
Nth term
What does n stand for?
no. of the term
What does d stand for?
Common difference
What does a stand for?
the 1st term
What are the equations for Sn ? (arithmetic series)
IN FORMULA BOOK
Sn = 1/2n (a+L)
Sn=1/2n{2a + (n-1)d}
What is the equation for Un in geometric series?
Un = ar^n-1
What is the equation for Sn in geometric series?
IN FORMULA BOOK
Sn = a(1 - r^n) / 1 - r
What is the sum to infinity?
IN FORMULA BOOK
S& = a / 1 - r
If IrI < 1 the sum will converge on a limit
If IrI > or equal to 1 the sum will diverge (separate)
