Math Problem Statement

Verify that the root of the equation x³ - 3x + 1 = 0 lies between 0 and 0.8

Solution

To verify that the root of the equation x33x+1=0x^3 - 3x + 1 = 0 lies between 0 and 0.8, we need to check the values of the function f(x)=x33x+1f(x) = x^3 - 3x + 1 at the endpoints of the interval. If the function changes sign between these points, then by the Intermediate Value Theorem, there is at least one root in this interval.

  1. Calculate f(0)f(0): f(0)=0330+1=1f(0) = 0^3 - 3 \cdot 0 + 1 = 1

  2. Calculate f(0.8)f(0.8): f(0.8)=(0.8)330.8+1=0.5122.4+1=0.888f(0.8) = (0.8)^3 - 3 \cdot 0.8 + 1 = 0.512 - 2.4 + 1 = -0.888

Now we observe:

  • f(0)=1f(0) = 1 (positive)
  • f(0.8)=0.888f(0.8) = -0.888 (negative)

Since f(0)f(0) is positive and f(0.8)f(0.8) is negative, the function f(x)=x33x+1f(x) = x^3 - 3x + 1 changes sign between x=0x = 0 and x=0.8x = 0.8. By the Intermediate Value Theorem, there is at least one root of the equation x33x+1=0x^3 - 3x + 1 = 0 in the interval (0,0.8)(0, 0.8).

Therefore, we have verified that a root of the equation lies between 0 and 0.8.

Would you like any additional details or have any questions?

Here are some related questions for further exploration:

  1. What is the exact value of the root in the interval (0,0.8)(0, 0.8)?
  2. How many roots does the equation x33x+1=0x^3 - 3x + 1 = 0 have in total?
  3. Can you find another interval where another root of x33x+1=0x^3 - 3x + 1 = 0 lies?
  4. How would you use Newton's method to approximate the root in the interval (0,0.8)(0, 0.8)?
  5. What does the graph of y=x33x+1y = x^3 - 3x + 1 look like?
  6. How would you determine the intervals where the function f(x)=x33x+1f(x) = x^3 - 3x + 1 is increasing or decreasing?
  7. What are the critical points of the function f(x)=x33x+1f(x) = x^3 - 3x + 1?
  8. How do you determine the concavity and inflection points of the function f(x)=x33x+1f(x) = x^3 - 3x + 1?

Tip: When verifying roots of a polynomial equation within a certain interval, always check the signs of the function values at the endpoints and apply the Intermediate Value Theorem for a thorough validation.

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Math Problem Analysis

Mathematical Concepts

Polynomial equations
Intermediate Value Theorem

Formulas

Function evaluation: f(x) = x^3 - 3x + 1

Theorems

Intermediate Value Theorem

Suitable Grade Level

Grades 11-12