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Ex 9.3, 5 - Chapter 9 Class 11 Sequences and Series - Part 4

Ex 9.3, 5 - Chapter 9 Class 11 Sequences and Series - Part 5

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Ex 9.3, 5 Which term of the following sequences: (b) (3,) 3, 3 3, is 729 ? (3,) 3, 3 3, . We know that an = arn 1 where an = nth term of GP n is the number of terms a is the first term r is the common ratio Here, first term a = 3 common ratio r = 3/ 3 = 3 nth term = 729 Putting values an = arn 1 729 = ( 3 ) ( 3 )^( 1) 729 = ( 3 )^(1+ 1) 729 = ( 3 )^ 3^6 = ( 3 )^ Squaring both sides (36)2 = ( 3)^2 36 2 = [( 3)^2 ]^ 312 = [3]^ Comparing powers 12 = n n = 12 Hence 12th term of GP is 729

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