Math Problem Statement

Use the Bisection method to find solutions accurate to within 10^-5 for the following problems: 3x - e^x = 0 for 1 ≤ x ≤ 2

Solution

To solve the equation 3xex=03x - e^x = 0 for 1x21 \leq x \leq 2 using the Bisection method to an accuracy of 10510^{-5}, we need to follow these steps:

Steps for Bisection Method:

  1. Define the function: Let f(x)=3xexf(x) = 3x - e^x.

  2. Initial Interval: The interval given is [1,2][1, 2]. We need to ensure that the function has opposite signs at the endpoints.

  3. Check Sign at Endpoints:

    • Calculate f(1)f(1) and f(2)f(2).
    • f(1)=3(1)e1=32.71828=0.28172f(1) = 3(1) - e^1 = 3 - 2.71828 = 0.28172.
    • f(2)=3(2)e2=67.38906=1.38906f(2) = 3(2) - e^2 = 6 - 7.38906 = -1.38906.

    Since f(1)>0f(1) > 0 and f(2)<0f(2) < 0, there is a root in the interval.

  4. Bisection Iteration:

    • Calculate the midpoint c=1+22=1.5c = \frac{1 + 2}{2} = 1.5.
    • Evaluate f(c)=f(1.5)=3(1.5)e1.5f(c) = f(1.5) = 3(1.5) - e^{1.5}.
    • Continue updating the interval depending on the sign of f(c)f(c) compared to the endpoints, and repeat until the interval is sufficiently small.

Let's perform the iterations numerically using Python to find the solution accurate to 10510^{-5}.The root of the equation 3xex=03x - e^x = 0 within the interval [1,2][1, 2] using the Bisection method, accurate to within 10510^{-5}, is approximately:

x1.51214x \approx 1.51214

The method took 16 iterations to converge to this result.

Questions to Consider:

  1. What are the advantages of the Bisection method compared to other root-finding methods?
  2. How would the convergence speed change if the interval were narrower initially?
  3. What are the implications if f(a)f(a) and f(b)f(b) are not of opposite signs?
  4. How does changing the tolerance affect the number of iterations?
  5. Can you apply the Bisection method to functions with multiple roots within the same interval?

Tip:

Always ensure that the function changes signs at the initial interval endpoints when using the Bisection method, as this guarantees the existence of a root within the interval.

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Math Problem Analysis

Mathematical Concepts

Numerical Methods
Bisection Method
Exponential Functions

Formulas

Bisection Method Formula: f(x) = 3x - e^x

Theorems

Intermediate Value Theorem

Suitable Grade Level

Undergraduate or Advanced High School (Grade 12)