C(n, k)

Definition

The term c(n, k), also known as the binomial coefficient, represents the number of ways to choose k elements from a set of n distinct elements without regard to the order of selection. This concept is fundamental in combinatorics and is directly linked to the binomial theorem, which expresses the expansion of powers of a binomial in terms of these coefficients. The notation is mathematically defined as $$c(n, k) = \frac{n!}{k!(n-k)!}$$, where '!' denotes factorial, which is the product of all positive integers up to that number.

5 Must Know Facts For Your Next Test

1. c(n, k) is only defined for non-negative integers n and k, where 0 \leq k \leq n.
2. The value of c(n, 0) is always 1 because there is exactly one way to choose zero elements from any set.
3. c(n, k) is symmetric; that is, c(n, k) = c(n, n-k), meaning choosing k elements from n is equivalent to leaving out n-k elements.
4. The sum of all the binomial coefficients for a given n equals 2^n; this can be represented as $$\sum_{k=0}^{n} c(n, k) = 2^n$$.
5. In combinatorial problems, c(n, k) can be used to solve real-world scenarios like forming committees or choosing subsets from larger groups.

Review Questions

• How can you derive the value of c(n, k) using factorials and why is this important?
  • The value of c(n, k) can be derived using the formula $$c(n, k) = \frac{n!}{k!(n-k)!}$$. This expression is important because it shows how many different ways you can choose k items from a total of n items without considering the order. Understanding this relationship allows us to apply combinatorial reasoning in various mathematical problems and real-life scenarios.
• Explain how Pascal's Triangle relates to binomial coefficients and provide an example.
  • Pascal's Triangle illustrates how binomial coefficients are arranged in a triangular format where each entry represents c(n, k). Each number is formed by adding the two numbers directly above it. For example, the third row corresponds to n=2: 1 (c(2, 0)), 2 (c(2, 1)), 1 (c(2, 2)). This visualization helps in understanding patterns within binomial coefficients and their calculations.
• Analyze the significance of the binomial theorem in relation to c(n, k) and its applications.
  • The binomial theorem establishes a powerful connection between algebra and combinatorics by stating that $(x+y)^n = \sum_{k=0}^{n} c(n,k)x^{n-k}y^k$. This theorem not only simplifies polynomial expansions but also shows how c(n, k) counts the number of ways to form terms when expanding a binomial expression. Its applications extend into probability theory and statistics where it aids in calculating probabilities in binomial distributions.

Related terms

Factorial: The product of all positive integers up to a given number n, denoted as n!, which is crucial for calculating binomial coefficients.

Pascal's Triangle: A triangular array of numbers where each number is the sum of the two directly above it, and the entries correspond to binomial coefficients.

Binomial Theorem: A formula that provides a method for expanding expressions raised to a power, using binomial coefficients to express each term in the expansion.