Chapter 9: Problem 74
In Exercises 71-76, write the first five terms of the sequence. (Assume that \( n \) begins with 0.) \( a_n = \dfrac{n^2}{(n + 1)!} \)
Short Answer
Expert verified
The first five terms of the sequence are: 0, 0.5, 0.66, 0.375, 0.133
Step by step solution
01
Substitute n=0 into sequence equation
When n=0, substitute 0 into the equation \( a_n = \dfrac{n^2}{(n + 1)!} \), we get \( a_0 = \dfrac{0^2}{(0 + 1)!}=\frac{0}{1}=0 \)
02
Substitute n=1 into sequence equation
When n=1, substitute 1 into the equation \( a_n = \dfrac{n^2}{(n + 1)!} \), we get \( a_1 = \dfrac{1^2}{(1 + 1)!}=\frac{1}{2}=0.5 \)
03
Substitute n=2 into sequence equation
When n=2, substitute 2 into the equation \( a_n = \dfrac{n^2}{(n + 1)!} \), we get \( a_2 = \dfrac{2^2}{(2 + 1)!}=\frac{4}{6}=0.\overline{66} \)
04
Substitute n=3 into sequence equation
When n=3, substitute 3 into the equation \( a_n = \dfrac{n^2}{(n + 1)!} \)(where ! represents factorial operation), we get \( a_3 = \dfrac{3^2}{(3 + 1)!}=\frac{9}{24}=0.375 \)
05
Substitute n=4 into sequence equation
When n=4, substitute 4 into the equation \( a_n = \dfrac{n^2}{(n + 1)!} \), we get \( a_4 = \dfrac{4^2}{(4 + 1)!}=\frac{16}{120}=0.133\overline{3} \)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Factorial
The concept of a factorial is essential in understanding sequences like the one given in the exercise. A factorial, denoted by the symbol \(!\), is a product of all positive integers up to a certain number. For instance, the factorial of 3, written as \(3!\), is calculated as \(3 \times 2 \times 1 = 6\). For every integer \(n\),
- \(0! = 1\) by definition
- \(1! = 1\)
- \(2! = 2 \times 1 = 2\)
- \(3! = 3 \times 2 \times 1 = 6\)
- and so forth.
Sequence Term Calculation for a Given Formula
Calculating each term of a sequence given a specific formula involves substituting values into the sequence's formula. The sequence we are examining is given by the expression:\[ a_n = \dfrac{n^2}{(n + 1)!} \]To find each term:
Substituting \(n = 1\) gives \(a_1 = \dfrac{1^2}{(1 + 1)!} = 0.5\), and so on.
Each substitution provides a clear view of individual terms in the sequence. It shows how changing \(n\) affects the outcome significantly, given the factorial growth in the denominator.
- Start with \(n = 0\) and substitute it into the formula.
- Continue replacing \(n\) with each subsequent integer until you have the desired number of terms.
Substituting \(n = 1\) gives \(a_1 = \dfrac{1^2}{(1 + 1)!} = 0.5\), and so on.
Each substitution provides a clear view of individual terms in the sequence. It shows how changing \(n\) affects the outcome significantly, given the factorial growth in the denominator.
Exploring Mathematical Sequences
A mathematical sequence is essentially a list of numbers ordered in a specific way according to a given rule or formula. This order can be crucial for discovering the nature and properties of the sequence. In this exercise, we are looking into a sequence defined by both a polynomial expression and a factorial in its denominator:
This specific kind of sequence
This specific kind of sequence
- shows a unique pattern as \(n\) increases.
- Factors like factorial in the denominator contribute to how fast the values decrease.
- Arithmetic (where there's a constant difference between terms)
- Geometric (where each term is a constant multiple of the previous)
- Other special forms like Fibonacci or alternating sequences.