geometric series and sequence

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

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