Series

Question 1

Arithmetic series formula for Un?

Answer 1

Un = a + (n-1)d

Question 2

Arithmetic series sum of formulas?

Answer 2

Sn = n/2 (2a + (n-1)d)

Sn = n/2(a + L)

Question 3

Geometric formula for Un?

Answer 3

Un = ar^(n-1)

Question 4

Geometric series sums formulae?

Answer 4

Sn = [a (1-r^n)] / (1-r)
Sum to infinity = a/(1-r)

Question 5

What are properties of increasing, decreasing and periodic series?

Answer 5

Increasing: next term greater than prev.
Decreasing: next term less than prev.
Periodic: if Un+k = Un and its period/order is k