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SUMMATION FORMULA - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • Summation by Sigma Operator is considered one the most difficult concept.

  • 16 Questions around this concept.

Solve by difficulty

Let f(x) be a function such that f(x+y)=f(x) \cdot f(y) for all x, y \in N if f(1)=3 and \sum_{\mathrm{k}=1}^{\mathrm{n}} \mathrm{f}(\mathrm{k})=3279 then the value of n is.

The sum of the first 20 terms of the series 5 + 11 + 19 + 29 + 41 + ….. is:

If  \mathrm{S}_{\mathrm{n}}=4+11+21+34+50+\ldots . to  \mathrm{n} terms, then \frac{1}{60}\left(\mathrm{~S}_{29}-\mathrm{S}_9\right)  is equal to

The value of $\lim _{n \rightarrow \infty} \sum_{k=1}^n \frac{n^3}{\left(n^2+k^2\right)\left(n^2+3 k^2\right)}$ is:

The sum of the series $\frac{1}{1-3 \cdot 1^2+1^4}+\frac{2}{1-3 \cdot 2^2+2^4}+\frac{3}{1-3 \cdot 3^2+3^4}+\ldots$ up to 10 -terms is

Concepts Covered - 0

Summation by Sigma Operator

Summation by Sigma(Σ) Operator 

The summation of each term of a sequence or a series can be represented in a compact form, called summation or sigma notation. This summation is represented by the Greek capital letter, Sigma (Σ).

For example, 

\\\mathrm{\sum_{n=1}^{n=10} n\;,\;it\;means \;the \;sum\;of\;n\;terms\;when\;n\;varies\;from\;1\;to\;10}\\\mathrm{\sum_{n=1}^{n=10} n=1+2+3+4+5+6+7+8+9+10}

 

Properties of Sigma Notation

\\\mathrm{1.\;\;\sum_{r=1}^{n}T_r=T_1+T_2+T_3+.......+T_n,\;where,\;T_r\;is\;the\;general\;term\;of\;the\;series.}\\\\\mathrm{2.\;\;\sum_{r=1}^{n}\left ( T_r\pm T_r' \right )=\sum_{r=1}^{n}T_r\pm\sum_{r=1}^{n}T_r'\;\;(sigma\;\;operator\;is\;distributive\;\;over\;addition\;and\;subtraction)}\\\\\mathrm{3.\;\;\sum_{r=1}^{n}T_rT_r'\neq\left ( \sum_{r=1}^{n}T_r \right )\left ( \sum_{r=1}^{n}T_r' \right )\;\;(sigma\;\;operator\;is\;not\;distributive\;\;over\;multiplication)}\\\\\mathrm{4.\;\;\sum_{r=1}^{n}\frac{T_r}{T_r'}\;\neq\;\frac{\sum_{r=1}^{n}T_r}{\sum_{r=1}^{n}T_r'}\;\;(sigma\;\;operator\;is\;not\;distributive\;\;over\;division})\\\\\mathrm{5.\;\;\sum_{r=1}^{n}aT_r=a\sum_{r=1}^{n}T_r\;\;\;\;(a\;is\;constant)}\\\\\mathrm{6.\;\;\sum_{j=1}^{n}\sum_{i=1}^{n}T_iT_j=\left ( \sum_{i=1}^{n}T_i \right )\left ( \sum_{j=1}^{n}T_j \right )\;\;\;(here\;i\;and\;j\;are\;independent)}

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