SOLUTION: In a geometric progression of positive terms, the 5th term is 9 times the 3rd term and the sum of the 6th and 7th terms is 972. Find the
a) common ratio
b) sum of the first 6 te
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-> SOLUTION: In a geometric progression of positive terms, the 5th term is 9 times the 3rd term and the sum of the 6th and 7th terms is 972. Find the
a) common ratio
b) sum of the first 6 te
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Question 880917: In a geometric progression of positive terms, the 5th term is 9 times the 3rd term and the sum of the 6th and 7th terms is 972. Find the
a) common ratio
b) sum of the first 6 terms Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website! a)
common ratio r=3
b)
Tn = T1 * r^(n - 1)
T7 = T1 * 3^(6)
T6 = T1 * 3^(5)
T7 +T6 =972
T1 * 3^(5)+ t * 3^(6)=972
T1*(3^5+3^6)=972
T1*243+729=972
T1*972=972
T1=1
S=T1*(1 - r^n)/(1 - r)
S=1*(1 - 3^6)/(1 - 3)
S=(1 - 3^6)/(1 - 3)
S=(1-729)/-2
S=-728/-2
S=364
