What is the sum of the geometric sequence –3, 18, –108, … if there are 8 terms?

Question

kingj · Answer

so the answer would be what

anonymous · Answer

that was the 18th term
and I think you would like to add all the terms?

anonymous · Answer

the nth term 

3*(-6)^17  =  -50779978334208

anonymous · Answer

not nth but 18th term

anonymous · Answer

the sum will be 

3*(-6)^0  + 3*(-6)^1 + 3*(-6)2...........  3(-6)^17

=> 3{ $$3{ \sum_{i=0}^{17}(-6)^{i}}$$

kingj · Answer

choices to chose from 
719,835 

 119,973 

 –119,973 

 –719,835

anonymous · Answer

since the odd ones will have negative values they should reduce the values.  Let me check the final summation given the above formula.

kingj · Answer

ok

kingj · Answer

what would be the final summation