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NCERT Class XI Mathematics - Sequences and Series - Solutions

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Question : 45
Total: 106
Evaluate
11
Σ
k=1
(2+3k)
Solution:  
11
Σ
k=1
(2+3k) = (2 + 3) + (2+32) + ... + (2+311)
= (2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2) + (31+32+...+311) = (2 × 11) + 3
(311−1)
3−1
= 22 +
3
2
(311−1)
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