Give step-by-step solution with explanation and final answer:1) (25pts.) The equation ¢* — 4x — 1 = 0 can be written in the form = g(x) in the following ways,
en — 1
ar = =, = 1 wa = Ina, +1), w=
Which sequence converges to the unique fixed point of the equation e* — 4x —1=0 in [1,2].
Use the convergent sequence to find zz by taking zo = 1.1.
Question:
Give step-by-step solution with explanation and final answer:1) (25pts.) The equation ¢* — 4x — 1 = 0 can be written in the form = g(x) in the following ways,
en — 1
ar = =, = 1 wa = Ina, +1), w=
Which sequence converges to the unique fixed point of the equation e* — 4x —1=0 in [1,2].
Use the convergent sequence to find zz by taking zo = 1.1.
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Asked by: sssssz
Created at: 2025-05-28 11:28:45
Final Answer:
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Let's solve the problem step by step:
### **Step 1: Rewrite the equation as fixed-point forms**
The equation is \( e^x - 4x - 1 = 0 \).
It is rewritten as \( x = g(x) \) in three ways:
1. \( x_{n+1} = e^{x_n} - 3x_n - 1 \)
2. \( x_{n+1} = \ln(4x_n + 1) \)
3. \( x_{n+1} = \frac{e^{x_n} - 1}{4} \)
---
### **Step 2: Determine which sequence converges**
We need to find which function \( g(x) \) will converge to the fixed point in the interval \([1, 2]\).
#### **Fixed Point Iteration Convergence**
A sufficient condition for convergence is that \(|g'(x)| < 1\) near the fixed point.
Let’s analyze each:
#### (a) \( g_1(x) = e^x - 3x - 1 \)
- \( g_1'(x) = e^x - 3 \)
- At \( x=1 \): \( e^1 - 3 \approx 2.718 - 3 = -0.282 \)
- At \( x=2 \): \( e^2 - 3 \approx 7.389 - 3 = 4.389 \)
- For \( x \) in \([1,2]\), \( g_1'(x) \) goes from negative to greater than 1, so **not always less than 1 in magnitude**.
#### (b) \( g_2(x) = \ln(4x + 1) \)
- \( g_2'(x) = \frac{4}{4x+1} \)
- At \( x=1 \): \( \frac{4}{5} = 0.8 \)
- At \( x=2 \): \( \frac{4}{9} \approx 0.444 \)
- For \( x \) in \([1,2]\), \( |g_2'(x)| < 1 \), so **this sequence will converge**.
#### (c) \( g_3(x) = \frac{e^x - 1}{4} \)
- \( g_3'(x) = \frac{e^x}{4} \)
- At \( x=1 \): \( \frac{2.718}{4} \approx 0.68 \)
- At \( x=2 \): \( \frac{7.389}{4} \approx 1.847 \)
- For \( x \) in \([1,2]\), \( g_3'(x) \) exceeds 1, so **may not always converge**.
**Conclusion:**
The convergent sequence is:
\[
x_{n+1} = \ln(4x_n + 1)
\]
---
### **Step 3: Find \( x_2 \) using \( x_0 = 1.1 \)**
Given \( x_0 = 1.1 \), compute \( x_1 \) and \( x_2 \):
#### Compute \( x_1 \):
\[
x_1 = \ln(4x_0 + 1) = \ln(4 \times 1.1 + 1) = \ln(4.4 + 1) = \ln(5.4)
\]
\[
x_1 \approx 1.686
\]
#### Compute \( x_2 \):
\[
x_2 = \ln(4x_1 + 1) = \ln(4 \times 1.686 + 1) = \ln(6.744 + 1) = \ln(7.744)
\]
\[
x_2 \approx 2.048
\]
---
## **Final Answers**
### **a) The sequence that converges is:**
\[
x_{n+1} = \ln(4x_n + 1)
\]
### **b) Using \( x_0 = 1.1 \), the value of \( x_2 \) is:**
\[
\boxed{2.048}
\]
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