NCERT Class XI Mathematics - Sequences and Series - Solutions

Question : 43

Total: 106

1, – a, a2, – a3 , ... n terms (if a ≠ – 1).

Solution:

In the given G.P., a = 1, r = – a and Sn =

a[1−rn]

1−r

, if |r| < 1
∴ Sn =

[1−(−a)n]

1+a

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