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Sequences and Series — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsSequences and Series2 Marks
Question
Find the indicated terms of the sequence, whose nth term is $a _ { n } = ( - 1 ) ^ { n - 1 } n ^ { 3 }; a_9$
✓

Answer

Given: $a_n = (-1)^{n-1} n^3$
$\therefore a _ { 9 } = ( - 1 ) ^ { 9 - 1 } \times ( 9 ) ^ { 3 } = ( - 1 ) ^ { 8 } \times 729 = 729$
Therefore, $9^{th}$ term is $729.$

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