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Method of Difference - Practice Questions & MCQ

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

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  • 12 Questions around this concept.

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The sum of the series

\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{3.4}-........upto\: \infty

is equal to:

 In a triangle \mathrm{A B C}, if \mathrm{A } is \mathrm{(1,2) } and medians through \mathrm{B } and \mathrm{C } are \mathrm{x+y=5} and \mathrm{x=4}  respectively, then \mathrm{B} is:

If $t_n$ denotes the $n^{\text {th }}$ term of the series $2+3+6+11+18+\ldots$ then $t_{50}$ is

The sum of

$(1^{2}-1+1)(1!)+(2^{2}-2+1)(2!)+...+(n^{2}-n+1)(n!)$

is

Let $\mathrm{S}_{\mathrm{n}}=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\ldots$ upto n terms. If the sum of the first six terms of an A.P. with first term p and common difference p is $\sqrt{2026 \mathrm{~S}_{2025}}$, then the absolute difference between $20^{\text {th }}$ and $15^{\text {th }}$ terms of the A.P. is

The value of $\lim _{n \rightarrow \infty}\left(\sum_{K=1}^n \frac{k^3+6 k^2+11 k+5}{(k+3)!}\right)$ is:

Concepts Covered - 1

METHOD OF DIFFERENCES (Shortcut)

METHOD OF DIFFERENCES (Shortcut)

To find the $\mathrm{n}^{\text {th }}$ term of the series, you can use the following steps:
If the sequence of the first consecutive difference is in A.P., then the $n^{\text {th }}$ term, $T_n=a n^2+b n+c$ or $a(n-1)(n-2)+b(n-1)+c$, where $a, b$ and $c$ are constants. To find the value of $a, b$ and $c$ put $n=1,2,3$ and put the value of $T_1, T_2, T_3$.

If the sequence of the first consecutive difference is in G.P., then the $n$th term, $T_n=a r^n+b$, where $a$ and $b$ are constant terms and $r$ is the common ratio of GP. To find the value of $a$ and $b$ put $n=1,2$ and put the value of $T_1, T_2$

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METHOD OF DIFFERENCES (Shortcut)

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