Pure - Series

Question 1

Formula for nth term of an arithmetic series:

Answer 1

• Un = a + (n - 1)d

a = first term
n = nth term
d = common difference

Question 2

Formula’s for sum of the first n terms of an arithmetic series”

Answer 2

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

a = first term
n = nth term
d = common difference
L = Last term

Question 3

Formula for nth term of a geometric sequence:

Answer 3

• Un = arⁿ⁻¹

a = first term
n = nth term
r = common ratio

Question 4

Formula for sum of first n terms of a geometric series:

Answer 4

Sn = a(1-rⁿ) / (1-r)

a = first term
n = nth term
r = common ratio

Question 5

Formula for the sum to infinity of a convergent geometric series:

Answer 5

S∞ = a / (1-r)

a = first term
r = common ratio