series formulae

Question 1

sum to infinity

Answer 1

a/(1- r)

Question 2

nth term of geometric series

Answer 2

ar^(n-1)

Question 3

sum of nth term of finite geometric series

Answer 3

a(1-r^n)/(1-r)

Question 4

sum of nth term of finite arithmetic series

Answer 4

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

Question 5

sum of nth term of finite arithemetic series including l

Answer 5

(n/2)(a+l)