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Eight numbers are in geometric progressi...

Eight numbers are in geometric progression. Their sum is 21 and the sum of their reciprocals is 7. Their product is :

A

243

B

32

C

81

D

162

Text Solution

Verified by Experts

The correct Answer is:
C
`a+ar..........+ar^(7)=21`
`"and" " "(1)/(a)+(1)/(ar)+.......+(1)/(ar^(7))=7impliesa^(2)r^(7)=3`
`therefore" "a^(8)r^(28)=81`
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  18. Let A =[(1,1,0),(0,1,0),(0,0,1)] and let I denote the 3xx3 identity ma...

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