Skip to main content
Ch. 10 - Infinite Sequences and Series
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 10, Problema 10.1.101

Recursively Defined Sequences
In Exercises 101–108, assume that each sequence converges and find its limit.
a₁ = 2,aₙ₊₁ = 72 / (1 + aₙ)

Guida verificata passo dopo passo
1
Identify the recursive sequence given: \(a_1 = 2\) and \(a_{n+1} = \frac{72}{1 + a_n}\). We want to find the limit \(L\) as \(n\) approaches infinity, assuming the sequence converges.
Assuming the sequence converges to a limit \(L\), then both \(a_n\) and \(a_{n+1}\) approach \(L\). So, set \(L = \frac{72}{1 + L}\).
Multiply both sides of the equation by \((1 + L)\) to clear the denominator: \(L(1 + L) = 72\).
Rewrite the equation as a quadratic: \(L^2 + L - 72 = 0\).
Solve the quadratic equation for \(L\) using the quadratic formula \(L = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\), where \(a=1\), \(b=1\), and \(c=-72\). Then determine which root makes sense in the context of the sequence.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
2m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Recursively Defined Sequences

A recursively defined sequence is one where each term is defined in terms of one or more previous terms. Understanding how to use the given initial term and the recursive formula is essential to generate terms and analyze the sequence's behavior.
Video consigliato:
6:40
Arithmetic Sequences - Recursive Formula

Convergence of Sequences

A sequence converges if its terms approach a specific finite value as the index goes to infinity. Determining convergence involves analyzing the recursive formula and checking if the sequence settles to a stable limit.
Video consigliato:
8:22
Introduction to Sequences

Finding the Limit of a Recursive Sequence

To find the limit of a convergent recursive sequence, assume the limit exists and set it equal to the expression defining the next term. Solving the resulting equation yields the limit, which represents the value the sequence approaches.
Video consigliato:
6:40
Arithmetic Sequences - Recursive Formula