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Ex 8.2, 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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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo