Math Problem Statement

Let f(x) = x³ - 3x - 1.5. Determine whether the Intermediate Value Theorem can be used to show that f(x) has a root in the interval (0, 1).

Solution

The problem concerns using the Intermediate Value Theorem (IVT) to determine if the function f(x)=x33x1.5f(x) = x^3 - 3x - 1.5 has a root in the interval (0,1)(0, 1). Let's solve it step by step:


Step 1: Intermediate Value Theorem Overview

The IVT states: If a function f(x)f(x) is continuous on a closed interval [a,b][a, b], and if f(a)f(a) and f(b)f(b) have opposite signs, then there exists at least one c(a,b)c \in (a, b) such that f(c)=0f(c) = 0.


Step 2: Verify Continuity

  1. Continuity of f(x)f(x): The function f(x)=x33x1.5f(x) = x^3 - 3x - 1.5 is a polynomial, which is continuous everywhere, including the interval [0,1][0, 1].

    Answer to i): ff is continuous on [0,1][0, 1].


Step 3: Evaluate f(0)f(0) and f(1)f(1)

We now calculate f(x)f(x) at the endpoints of the interval:

  1. f(0)=(0)33(0)1.5=1.5f(0) = (0)^3 - 3(0) - 1.5 = -1.5
  2. f(1)=(1)33(1)1.5=131.5=3.5f(1) = (1)^3 - 3(1) - 1.5 = 1 - 3 - 1.5 = -3.5

Step 4: Check Opposite Signs

  1. The signs of f(0)=1.5f(0) = -1.5 and f(1)=3.5f(1) = -3.5 are the same (both negative). Therefore, f(x)f(x) does not satisfy the condition of the IVT (having opposite signs at the endpoints).

Final Answer

Since f(x)f(x) does not meet the necessary conditions for the Intermediate Value Theorem, we cannot use IVT to show that f(x)f(x) has a root in (0,1)(0, 1).

Would you like me to explore this further or address related questions?


Related Questions to Explore:

  1. What is the Intermediate Value Theorem, and why is continuity crucial for it?
  2. How would the conclusion change if f(0)f(0) and f(1)f(1) had opposite signs?
  3. Can we graph f(x)=x33x1.5f(x) = x^3 - 3x - 1.5 to verify its behavior in (0,1)(0, 1)?
  4. Are there numerical methods (e.g., Newton's Method) to find roots of f(x)f(x)?
  5. How does polynomial continuity ensure f(x)f(x) behaves predictably?

Tip:

When applying the Intermediate Value Theorem, always ensure that the function is continuous and check the signs of f(a)f(a) and f(b)f(b) to confirm they are opposite.

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Math Problem Analysis

Mathematical Concepts

Algebra
Calculus
Continuity
Roots of Functions

Formulas

f(x) = x³ - 3x - 1.5

Theorems

Intermediate Value Theorem

Suitable Grade Level

Grades 11-12