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Consider the sequence \(1,2,6,24,120, \ldots\) (a) List the next two terms of the seguence. (b) Assuming the sequence is denoted by \(A_{1}, A_{2}, A_{3}, \ldots,\) give an explicit formula for \(A_{N}\). (c) Assuming the sequence is denoted by \(P_{0}, P_{1}, P_{2}, \ldots\) give an explicit formula for \(P_{\mathrm{y}}\)

Short Answer

Expert verified
The next two terms are 720 (6!) and 5040 (7!). The explicit formula for A_N is A_N = N!. The explicit formula for P_y is P_y = (y+1)!.

Step by step solution

01

Identify the Pattern

Analyze the given terms of the sequence to understand the pattern. Each term seems to be a factorial of its position in the sequence. The pattern shows that each number is a product of all positive integers up to that number: 1 = 1! = 12 = 2! = 1 * 26 = 3! = 1 * 2 * 324 = 4! = 1 * 2 * 3 * 4120 = 5! = 1 * 2 * 3 * 4 * 5.
02

Find the Next Two Terms

To find the next two terms, continue the pattern by calculating the next two factorials. The sixth term, which is the factorial of 6 (6!), is 1 * 2 * 3 * 4 * 5 * 6 = 720. The seventh term is the factorial of 7 (7!), which is 1 * 2 * 3 * 4 * 5 * 6 * 7 = 5040.
03

Create the Explicit Formula for A_N

Observing the pattern, we see that the nth term, denoted by A_N, is the factorial of N. In mathematical terms, A_N is expressed as the product of all positive integers up to N, so the formula is A_N = N!.
04

Translate A_N to P_y

To denote the sequence as \(P_0, P_1, P_2, \ldots\), we adjust the term numbering starting from 0. Therefore, P_y corresponds to the (y+1)th term of the original sequence. The explicit formula for P_y, considering the yth term is actually the (y+1) factorial, is P_y = (y+1)!.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Mathematical Sequences
A mathematical sequence is a collection of numbers that follow a specific pattern or a set of rules. Each number in the sequence is called a term. When looking at sequences like 1,2,6,24,120, \(\ldots\), it’s crucial to identify how each term is derived from the previous one or its position in the series.

The sequence in our example reflects a specific relationship between consecutive terms, indicating that a common operation is performed repeatedly. Understanding this concept is key to uncovering the pattern and predicting subsequent terms, which is often integral to solving problems involving sequences.
Explicit Formula
In mathematics, finding an explicit formula for a sequence is a way to express the nth term directly in relation to n, without reference to other terms. Such a formula allows one to compute any term in the sequence without having to know the previous ones. For the sequence given in the exercise, the explicit formula lets us calculate any term A_N or P_y instantly by plugging in the value of N or y into the formula A_N = N! or P_y = (y+1)!.

Benefits of an Explicit Formula

  • It simplifies the computation of far-reaching terms.
  • It aids in analyzing the sequence behavior as it progresses.
  • It makes pattern recognition easier.
An explicit formula is an invaluable tool when working with sequences as it encapsulates the essence of the pattern in a concise mathematical expression.
Factorials
Factorials are mathematical expressions that represent the product of an integer and all the positive integers below it, down to 1. Denoted by an exclamation mark (e.g., 5!), it is read as '5 factorial' and calculated as 5! = 5 \(\times\) 4 \(\times\) 3 \(\times\) 2 \(\times\) 1 = 120. Factorials grow very quickly in value as the integer increases.

Factorials are fundamental in various fields such as calculus, algebra, and especially in permutations and combinations, which are significant in statistics and probability theory. Recognizing a factorial sequence is an integral step in understanding complex mathematical concepts and solving related problems effectively.
Pattern Recognition in Sequences
Recognizing the pattern in a sequence involves identifying the rule or rules that govern the creation of the terms. Pattern recognition is the first step in understanding a sequence and establishing an explicit formula. Let’s break down two common pattern types:

Arithmetic Sequences

These involve adding or subtracting a constant value to obtain subsequent terms.

Geometric Sequences

In these sequences, terms are multiplied or divided by a set value.

The given sequence of factorials represents another pattern type involving operations on an entire set of preceding integers. By mastering pattern recognition, students can discern the sequential structure and predict future terms, which is critical in advancing mathematical learning and application.

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