Series

Question 1

Sum of an Arithmetic Series

Answer 1

Sₙ=(n/2)(a1+aₙ),

n=number of terms, a1=first term, aₙ=nth term

Question 2

Sum of First n Terms of Geometric Series

Answer 2

a1(1-rⁿ)/(1-r)

a1=first term, r=common ration

Question 3

Sum of Infinite Geometric Series

Answer 3

a1/(1-r) with |r| < 1
a1=first term, r=common ratio

Question 4

Sum of First n Odd/Even Integers

Answer 4

First n odd numbers: n², First n even numbers: n(n+1)

Question 5

Number of Terms in Arithmetic Sequence

Answer 5

aₙ = a1+(n-1)d
Solve for n.

d=common difference(pay attention to sign)