SOLUTION: Find the sum of each geometric series described 1. asub1= 512 r=1/2 n=6 2. 3 + 6 + 12...+192 3. asub1= -2 asub5= -162 n=7

Algebra ->  Sequences-and-series -> SOLUTION: Find the sum of each geometric series described 1. asub1= 512 r=1/2 n=6 2. 3 + 6 + 12...+192 3. asub1= -2 asub5= -162 n=7       Log On


   

Question 65392: Find the sum of each geometric series described
1. asub1= 512 r=1/2 n=6
2. 3 + 6 + 12...+192
3. asub1= -2 asub5= -162 n=7
Answer by venugopalramana(3286) About Me  (Show Source):
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Find the sum of each geometric series described
1. asub1= 512 r=1/2 n=6
SN=A1/(1-R)
=512/[1-1/2]= 1008
2. 3 + 6 + 12...+192
A1=3.....R=6/3=2.....AN=192
AN = A1*R^(N-1)
192=3*(2)^(N-1)
2^(N-1)=192/3=64=2^6
N-1=6
N=7
SN = 3[2^7-1]/(2-1)=381
3. asub1= -2 asub5= -162 n=7
A5=A1*R^(5-1)
-162=-2*R^4
R^4=162/2=81=3^4
R=3
S7 = -2[3^7-1]/(3-1)=-2186