ARITHMETIC SERIES GEOMETRIC SERIES
The sum of the terms in a sequence is known as a series and is denoted by Sn
A formula is used when it is not practical to find the sum of many terms
Terminology common to both AP and GP:
T1; T2; T3; T4; …; Tn is a sequence to n-terms
T1 + T2 + T3 + T4 +…+ Tn is a series of n-terms
S1 = T1 is the sum of one term
S2 = T1 + T2 is the sum of the first two terms
Sn = T1 + T2 + T3 + T4 +…+ Tn is the sum of the first n terms
Formula: Formula:
n a(r ⁿ−1)
Sn = [2a=(n-1)d] Sn = ;r=1
2 r −1
OR:
n
Sn = (a+l)
2
l is the last term of the sequence, so this formula
can only be used when the last term is given (or you
are able to calculate the last term)
The sum of the terms in a sequence is known as a series and is denoted by Sn
A formula is used when it is not practical to find the sum of many terms
Terminology common to both AP and GP:
T1; T2; T3; T4; …; Tn is a sequence to n-terms
T1 + T2 + T3 + T4 +…+ Tn is a series of n-terms
S1 = T1 is the sum of one term
S2 = T1 + T2 is the sum of the first two terms
Sn = T1 + T2 + T3 + T4 +…+ Tn is the sum of the first n terms
Formula: Formula:
n a(r ⁿ−1)
Sn = [2a=(n-1)d] Sn = ;r=1
2 r −1
OR:
n
Sn = (a+l)
2
l is the last term of the sequence, so this formula
can only be used when the last term is given (or you
are able to calculate the last term)
