# How do you find the sum of the infinite geometric series #Sigma -3(0.9)^n# from n=0 to #oo#?

##### 1 Answer

Jun 18, 2017

#### Answer:

# S = sum_(n=0)^oo -3(0.9)^n = -30#

#### Explanation:

The sum:

# S = sum_(n=0)^oo -3(0.9)^n#

represents a GP with

# s_oo = a/(1-r) #

Which gives us:

# S = (-3)/(1-0.9) #

# \ \ = (-3)/(0.1) #

# \ \ = -30 #