What is the sum of the geometric sequence 1, 3, 9, … if there are 14 terms

Question

campbell_st · Answer

well the 1st term is a = 1 the common ratio is r = 3 and the number of terms n = 19

so you need to substitute them into the formula 

$$S_{n} = \frac{a(r^n - 1)}{r - 1} $$

to get the answer

anonymous · Answer

?

anonymous · Answer

plz explain in depth

campbell_st · Answer

do you understand common ratio...

anonymous · Answer

cause i ain't getting the answer 
and yeah

campbell_st · Answer

ok... so here is the substitution 

$$S_{19} = \frac{1 \times ( 3^{19} - 1)}{ 3 - 1}$$

now evaluate

anonymous · Answer

were do you get 19 from ???

campbell_st · Answer

oops that should be 14

$$S_{14} = \frac{ 1 \times (3^{14} - 1)}{3 -1}$$

anonymous · Answer

yeah can you give me the answer i am trying it and doesn't seem right

campbell_st · Answer

here's a calculator that may help http://web2.0calc.com/

anonymous · Answer

i have a graphing cal and a scientific still formual isn't comeing out  right for my multiple choice

anonymous · Answer

1,285,956 

 2,391,484 

 3,556,228 

 4,287,382

campbell_st · Answer

all you need to do on you calculator is enterit as its written below

$$1 \times (3^{14} -1)\div(3 -1)$$

then press equals..

anonymous · Answer

thanks 
for being little more clear

anonymous · Answer

Ty!! :) This was exaplained really clear, just simplfy 1*(3^14-1)/(3-1) :D