Chapter 3: Problem 7
Start from \(x_{0}=6\) and \(x_{0}=2\). Compute \(x_{1}, x_{2}, \ldots\) to test convergence: $$ x_{n+1}=\frac{1}{2} x_{n}-1 $$
Short Answer
Expert verified
Both sequences converge, with \(x_0 = 6\) converging starting from \(x_3\) and \(x_0 = 2\) steadily decreasing.
Step by step solution
01
Apply Recurrence Formula for Initial Values
We start with the initial values given, which are \(x_0 = 6\) and \(x_0 = 2\). We apply the recurrence formula \(x_{n+1} = \frac{1}{2} x_n - 1\) to compute the next term \(x_1\).
02
Compute Next Term for \(x_0 = 6\)
Substitute \(x_0 = 6\) into the formula \(x_{n+1} = \frac{1}{2} x_n - 1\): \[ x_1 = \frac{1}{2} \cdot 6 - 1 = 3 - 1 = 2 \]So, \(x_1 = 2\).
03
Compute Next Term for \(x_0 = 2\)
Substitute \(x_0 = 2\) into the same formula:\[ x_1 = \frac{1}{2} \cdot 2 - 1 = 1 - 1 = 0 \]So, \(x_1 = 0\).
04
Continue Applying Recurrence for Further Terms, \(x_0 = 6\) Sequence
Now apply the formula to find \(x_2\):\[ x_2 = \frac{1}{2} \cdot 2 - 1 = 1 - 1 = 0 \]Continue for \(x_3\):\[ x_3 = \frac{1}{2} \cdot 0 - 1 = 0 - 1 = -1 \]
05
Continue Applying Recurrence for Further Terms, \(x_0 = 2\) Sequence
For the sequence starting with \(x_0 = 2\), find \(x_2\):\[ x_2 = \frac{1}{2} \cdot 0 - 1 = 0 - 1 = -1 \]And \(x_3\):\[ x_3 = \frac{1}{2} \cdot (-1) - 1 = -0.5 - 1 = -1.5 \]
06
Analyze Convergence
Observe that the sequence for \(x_0 = 6\) approached -1 starting from \(x_3\). Similarly, the sequence from \(x_0 = 2\) is also approaching a closer negative value and continues decreasing. Both sequences converge towards negative values.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Convergence Testing
Convergence testing helps us determine if a sequence approaches a specific value as it is extended. It is essential to analyze whether terms within the sequence become closer to a particular number or if they continue to fluctuate without settling down. In our exercise, convergence testing was achieved by continuing the sequence calculation and observing the trend.
- The starting term in both sequences have different initial conditions, creating diverse paths of convergence.
- As we apply the recurrence relation repeatedly, the sequences seem to approach a certain value indicating convergence.
- For example, in the sequence starting from 6, the terms quickly shift towards -1 by the third term and stabilize, suggesting a convergence towards this number.
Sequence Computation
Sequence computation involves generating subsequent numbers in a sequence using a specific formula or process. This exercise uses a recurrence relation to compute each next term based on the previous one.
- Starting from an initial value, here given as 6 or 2, the recurrence formula \(x_{n+1} = \frac{1}{2}x_n - 1\) is applied.
- This pattern reveals subsequent terms, which are calculated step-by-step until a specific part of the sequence is obtained.
- The computation shows how changing the initial value affects the resulting sequence pattern.
Initial Conditions
Initial conditions are the starting values given in a sequence problem that significantly impact the resulting behavior of the sequence. In our exercise, these conditions were \(x_0 = 6\) and \(x_0 = 2\).
- The choice of initial conditions can lead to entirely different sequences, even with an identical recurrence relation as seen here.
- For \(x_0 = 6\), the sequence diminished towards -1, different compared to the sequence starting from \(x_0 = 2\).
- These initial conditions provide the initial step needed to initiate calculations and direct how the sequence develops over time.