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Recent questions tagged binomial-theorem

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TIFR CSE 2022 | Part B | Question: 9
Let $n \geq 2$ be any integer. Which of the following statements is $\text{FALSE}?$ $n!$ divides the product of any $n$ consecutive integers $\displaystyle{}\sum_{i=0}^n\left(\begin{array}{c}n \\ i\end{array}\right)=2^n$ ... an odd prime, then $n$ divides $2^{n-1}-1$ $n$ divides $\left(\begin{array}{c}2 n \\ n\end{array}\right)$

admin asked in Combinatory Sep 1, 2022

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TIFR CSE 2021 | Part A | Question: 10
Lavanya and Ketak each flip a fair coin (i.e., both heads and tails have equal probability of appearing) $n$ times. What is the probability that Lavanya sees more heads than ketak? In the following, the binomial coefficient $\binom{n}{k}$ counts the number of $k$-element subsets of ... $\sum_{i=0}^{n}\frac{\binom{n}{i}}{2^{n}}$

soujanyareddy13 asked in Probability Mar 25, 2021

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TIFR CSE 2021 | Part A | Question: 12
How many numbers in the range ${0, 1, \dots , 1365}$ have exactly four $1$'s in their binary representation? (Hint: $1365_{10}$ is $10101010101_{2}$, that is, $1365=2^{10} + 2^{8}+2^{6}+2^{4}+2^{2}+2^{0}.)$ ... $\binom{11}{4}+\binom{9}{3}+\binom{7}{2}+\binom{5}{1}$ $1024$

soujanyareddy13 asked in Digital Logic Mar 25, 2021

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Kenneth Rosen Edition 7 Exercise 6.4 Question 39 (Page No. 422 - 423)
Determine a formula involving binomial coefficients for the nth term of a sequence if its initial terms are those listed. [Hint: Looking at Pascal's triangle will be helpful. Although infinitely many sequences start with a specified set of terms, ... $1, 3, 15, 84, 495, 3003, 18564, 116280, 735471, 4686825,\dots$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 38 (Page No. 422)
Give a combinatorial proof that if n is a positive integer then $\displaystyle\sum_{k = 0}^{n} k^{2} \binom{n} {k} = n(n + 1)2^{n−2}.$ [Hint: Show that both sides count the ways to select a subset of a set of ... necessarily distinct elements from this subset. Furthermore, express the right-hand side as $n(n − 1)2^{n−2} + n2^{n−1}.]$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 37 (Page No. 422)
Use question $33$ to prove the hockeystick identity from question $27.$ [Hint: First, note that the number of paths from $(0, 0)\: \text{to}\: (n + 1,r)$ equals $\binom{n + 1 + r}{r}.$ Second, count the number of paths by summing the number of these paths that start by going $k$ units upward for $k = 0, 1, 2,\dots,r.]$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 36 (Page No. 422)
Use question $33$ to prove Pascal’s identity. [Hint: Show that a path of the type described in question $33$ from $(0, 0)\: \text{to}\: (n + 1 − k, k)$ passes through either $(n + 1 − k, k − 1)\: \text{or} \:(n − k, k),$ but not through both.]

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 35 (Page No. 422)
Use question $33$ to prove Theorem $4.$ [Hint: Count the number of paths with n steps of the type described in question $33.$ Every such path must end at one of the points $(n − k, k)\:\text{for}\: k = 0, 1, 2,\dots,n.]$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 34 (Page No. 422)
Use question $33$ to give an alternative proof of Corollary $2$ in Section $6.3,$ which states that $\binom{n}{k} = \binom{n}{n−k} $ whenever $k$ is an integer with $0 \leq k \leq n.[$Hint: Consider the number of paths of the type described in question $33$ ... $(0, 0)\: \text{to}\:(k, n − k).]$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 33 (Page No. 422)
In this exercise we will count the number of paths in the $xy$ plane between the origin $(0, 0)$ and point $(m, n),$ where $m$ and $n$ are nonnegative integers, such that each path is made up of a series of steps, where each ... move one unit upward. Conclude from part $(A)$ that there are $\binom{m + n}{n}$ paths of the desired type.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 32 (Page No. 422)
Prove the binomial theorem using mathematical induction.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 31 (Page No. 422)
Show that a nonempty set has the same number of subsets with an odd number of elements as it does subsets with an even number of elements.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 30 (Page No. 422)
Give a combinatorial proof that $\displaystyle{}\sum_{k = 1}^{n} k \binom{n}{k}^{2} = n \binom{2n−1}{n−1}.$ [Hint: Count in two ways the number of ways to select a committee, with $n$ members ... of $n$ mathematics professors and $n$ computer science professors, such that the chairperson of the committee is a mathematics professor.]

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 29 (Page No. 422)
Give a combinatorial proof that $\displaystyle{}\sum_{k = 1}^{n} k \binom{n}{k} = n2^{n−1}.$ [Hint: Count in two ways the number of ways to select a committee and to then select a leader of the committee.]

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 28 (Page No. 422)
Show that if $n$ is a positive integer, then $\binom{2n}{2} = 2\binom{n}{2} + n^{2} $ using a combinatorial argument. by algebraic manipulation.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 27 (Page No. 422)
Prove the hockeystick identity $\displaystyle{}\sum_{k=0}^{r} \binom{n + k}{k} = \binom{n + r + 1}{r}$ whenever $n$ and $r$ are positive integers, using a combinatorial argument. using Pascal’s identity.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 26 (Page No. 422)
Let $n$ and $k$ be integers with $1 \leq k \leq n.$ Show that $\displaystyle{}\sum_{k=1}^{n} \binom{n}{k}\binom{n}{k − 1} = \dfrac{\binom{2n + 2}{n + 1}}{2} − \binom{2n}{n}.$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 25 (Page No. 422)
Let n be a positive integer. Show that $\binom{2n}{n + 1} + \binom{2n}{n} = \dfrac{\binom{2n + 2}{n + 1}}{2}.$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 24 (Page No. 422)
Show that if $p$ is a prime and $k$ is an integer such that $1 \leq k \leq p − 1,$ then $p$ divides $\binom{p}{k} .$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 23 (Page No. 422)
Show that if $n$ and $k$ are positive integers, then $\binom{n + 1}{k} = \dfrac{(n + 1)\binom {n}{k – 1}}{k}.$ Use this identity to construct an inductive definition of the binomial coefficients.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 22 (Page No. 422)
Prove the identity $\binom{n}{r}\binom{r}{k} = \binom{n}{k}\binom{n−k}{r−k} ,$ whenever $n, r,$ and $k$ are nonnegative integers with $r \leq n$ and $k \leq r,$ using a combinatorial argument. using an argument based on the formula for the number of $r$-combinations of a set with $n$ elements.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 21 (Page No. 422)
Prove that if $n$ and $k$ are integers with $1 \leq k \leq n,$ then $k \binom{n}{k} = n \binom{n−1}{k−1},$ using a combinatorial proof. [Hint: Show that the two sides of the identity count the number of ways to select ... subset.] using an algebraic proof based on the formula for $\binom{n}{r}$ given in Theorem $2$ in Section $6.3.$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 20 (Page No. 421)
Suppose that $k$ and $n$ are integers with $1 \leq k<n.$ Prove the hexagon identity $\binom{n-1}{k-1}\binom{n}{k+1}\binom{n+1}{k} = \binom{n-1}{k}\binom{n}{k-1}\binom{n+1}{k+1},$ which relates terms in Pascal’s triangle that form a hexagon.

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 19 (Page No. 421)
Prove Pascal’s identity, using the formula for $\binom{n}{r}.$

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 18 (Page No. 421)
Suppose that $b$ is an integer with $b \geq 7.$ Use the binomial theorem and the appropriate row of Pascal’s triangle to find the base-$b$ expansion of $(11)^{4}_{b}$ [that is, the fourth power of the number $(11)_{b}$ in base-$b$ notation].

admin asked in Combinatory Apr 30, 2020

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Kenneth Rosen Edition 7 Exercise 6.4 Question 17 (Page No. 421)
Show that if $n$ and $k$ are integers with $1 \leq k \leq n,$ then $\binom{n}{k} \leq \frac{n^{k}}{2^{k−1}}.$

admin asked in Combinatory Apr 30, 2020

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