Test Index

NCERT Class XI Mathematics - Sequences and Series - Solutions

© examsnet.com
Question : 45 of 106
Marks: +1, -0
Evaluate ∑k=111(2+3k)\sum\limits_{k=1}^{11} (2+3^k)
Solution:  
∑k=111(2+3k)\sum\limits_{k=1}^{11} (2+3^k) = (2 + 3) + (2+32)(2+3^2) + ... + (2+311)(2+3^{11})
= (2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2) + (31+32+⋯+311)(3^1+3^2+\dots+3^{11}) = (2 × 11) + 3 (311−1)3−1\frac{(3^{11}-1)}{3-1}
= 22 + 32(311−1)\frac{3}{2}(3^{11}-1)
© examsnet.com
Go to Question:
Prev Question
Next Question