Geometric Series

Evaluate the geometric series described.
 $3+15+75+375...,\ \ \ \ n=6$  

Evaluate the geometric series $1-2+4-8,\ ...,\ \ \ \ \ \ \ n=8$  

 $a_1=-2,\ \ \ r=-2,\ \ \ S_n=22$  Determine the number of terms n in the series

Evaluate  $\sum_{k\ =\ 1}^7\left(-2\right)^{k\ -1\ }$  

 $a_1=3,\ \ \ r=5,\ \ \ n=7$  Evaluate

 $Evaluate\ \ \ \ \ \sum_{i\ =1}^9-3\cdot3^{\ \left(i-1\right)}$  

 $-3,\ \ 6,\ -12,\ \ 24,\ ....$  Find the common ratio

 $-4,\ -12,\ -36,\ -108,\ ...$  Find the common ratio

 $4,\ 24,\ 144,\ 864,\ ...$  Find the next 3 terms

 $1,\ -2,\ 4,\ -8,\ ...\ \ Find\ a_{11}$