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Binomial Expansion and Factorial Notation
The binomial theorem describes the algebraic expansion of powers of a binomial.
Learning Objective

Use factorial notation and Pascal's Triangle to find the coefficients of a binomial expansion
Key Points
 According to the theorem, it is possible to expand the power (x + y)n into a sum involving terms of the form a^{x}b^{y}c, where the exponents b and c are nonnegative integers with b + c = n, and the coefficient a of each term is a specific positive integer depending on n and b.
 The factorial of a nonnegative integer n, denoted by n!, is the product of all positive integers less than or equal to n.
 Binomial coefficients can be written as
$_{n}{C}_{k}$ and are defined in terms of the factorial function n!.
Term

factorial
The result of multiplying a given number of consecutive integers from 1 to the given number. In equations, it is symbolized by an exclamation mark (!). For example, 5! = 1 * 2 * 3 * 4 * 5 = 120.
Full Text
The binomial theorem describes the algebraic expansion of powers of a binomial. According to the theorem, it is possible to expand the power (x + y)^{n} into a sum involving terms of the form a^{x}b^{y}c, where the exponents b and c are nonnegative integers with b + c = n, and the coefficient a of each term is a specific positive integer depending on n and b. When an exponent is zero, the corresponding power is usually omitted from the term.
In mathematics, the factorial of a nonnegative integer n, denoted by n!, is the product of all positive integers less than or equal to n . For example,
Factorials
The first few and selected larger members of the sequence of factorials (sequence A000142 in OEIS). The values specified in scientific notation are rounded to the displayed precision.
The value of 0! is 1, according to the convention for an empty product. The factorial operation is encountered in many different areas of mathematics, notably in combinatorics, algebra, and mathematical analysis. Its most basic occurrence is the fact that there are n! ways to arrange n distinct objects into a sequence (i.e., permutations of the set of objects). The definition of the factorial function can also be extended to noninteger arguments, while retaining its most important properties; this involves more advanced mathematics, notably techniques from mathematical analysis.
The coefficients that appear in the binomial expansion are called binomial coefficients. These are usually written
The coefficient of x^{n−k}y^{k} is given by the formula:
Note that, although this formula involves a fraction, the binomial coefficient
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Key Term Reference
 binomial
 Appears in these related concepts: Sums, Differences, Products, and Quotients, Factoring Trinomials of the Form ax^2 + bx + c; Perfect Squares, and Special Factorizations and Binomials
 binomial coefficient
 Appears in these related concepts: Total Number of Subsets, Combinations, and Binomial Expansions and Pascal's Triangle
 coefficient
 Appears in these related concepts: Trinomials of the Form ax^2 + bx + c, Where a is Not Equal to 1, Balancing Chemical Equations, and Polynomials: Introduction, Addition, and Subtraction
 exponent
 Appears in these related concepts: Logarithms of Powers, Scientific Notation, and Logarithms of Quotients
 fraction
 Appears in these related concepts: SI Unit Prefixes, Separable Equations, and Fractions
 function
 Appears in these related concepts: Inverse Functions, Average Value of a Function, and Functions and Their Notation
 integer
 Appears in these related concepts: Exact Numbers, Scientific Notation, and Finding a Specific Term
 operation
 Appears in these related concepts: Outsourcing, Designing the Operation, and Integer Exponents
 permutation
 Appears in these related concepts: Permutations, Permutations: Notation; n Objects Taken k at a Time, and Permutations of Nondistinguishable Objects
 sequence
 Appears in these related concepts: Summing an Infinite Series, Introduction to Sequences, and Finding the General Term
 set
 Appears in these related concepts: Sequences, Expressions and Sets of Numbers, and Executive Function and Control
 term
 Appears in these related concepts: Arithmetic Sequences, Basics of Graphing Polynomial Functions, and The 22nd Amendment
 zero
 Appears in these related concepts: The Discriminant, Finding Zeroes of Factored Polynomials, and Reducing Equations to a Quadratic
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Source: Boundless. “Binomial Expansion and Factorial Notation.” Boundless Algebra. Boundless, 21 Jul. 2015. Retrieved 06 Feb. 2016 from https://www.boundless.com/algebra/textbooks/boundlessalgebratextbook/sequencesseriesandcombinatorics8/thebinomialtheorem58/binomialexpansionandfactorialnotation24311213/