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NCERT Class XI Mathematics - Sequences and Series - Solutions

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Question : 9 of 106
Marks: +1, -0
ana_n = (−1)n−1n3;a9(-1)^{n-1} n^3 ;a_9
Solution:  
We have, ana_n = (−1)n−1n3;a9(-1)^{n-1} n^3 ;a_9
Put n = 9, a9a_9 = (−1)9−1(9)3(-1)^{9-1} (9)^3 = (−1)8(729)(-1)^8 (729) = 729
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