Math Problem Statement

Use the Intermediate Value Theorem to show that the following equation has a solution on the given interval: x^3 + x + 3 = 0; Interval: (-2,1). Evaluate the function at the endpoints and illustrate the solution with a graph.

Solution

Let's break down the problem from the image step by step:

a. Intermediate Value Theorem (IVT) Application:

The problem asks you to apply the Intermediate Value Theorem (IVT) to show that the equation x3+x+3=0x^3 + x + 3 = 0 has a solution in the interval (2,1)(-2, 1).

The Intermediate Value Theorem states:

  • If f(x)f(x) is continuous on a closed interval [a,b][a, b],
  • And NN is a value strictly between f(a)f(a) and f(b)f(b),
  • Then there is at least one c(a,b)c \in (a, b) such that f(c)=Nf(c) = N.

Here, the function is f(x)=x3+x+3f(x) = x^3 + x + 3, and we are given the interval (2,1)(-2, 1).

Step 1: Check Continuity

The function f(x)=x3+x+3f(x) = x^3 + x + 3 is a polynomial, and polynomials are continuous everywhere, so it's continuous on (2,1)(-2, 1). This satisfies the first condition of the IVT.

Step 2: Evaluate the Function at the Endpoints

Evaluate f(x)f(x) at x=2x = -2 and x=1x = 1:

  • f(2)=(2)3+(2)+3=82+3=7f(-2) = (-2)^3 + (-2) + 3 = -8 - 2 + 3 = -7
  • f(1)=(1)3+1+3=1+1+3=5f(1) = (1)^3 + 1 + 3 = 1 + 1 + 3 = 5

Now we have:

  • f(2)=7f(-2) = -7
  • f(1)=5f(1) = 5

Step 3: Apply IVT

Since f(2)=7f(-2) = -7 and f(1)=5f(1) = 5, and 0 lies between -7 and 5, by the Intermediate Value Theorem, there exists at least one c(2,1)c \in (-2, 1) such that f(c)=0f(c) = 0. Therefore, the equation x3+x+3=0x^3 + x + 3 = 0 has a solution in this interval.

b. Graphing Utility and Solutions

To find the exact solution(s), you can use a graphing calculator or utility to graph the function f(x)=x3+x+3f(x) = x^3 + x + 3 and identify where the graph crosses the x-axis (i.e., where f(x)=0f(x) = 0) in the interval (2,1)(-2, 1).

c. Graph Illustration

Once the function is graphed, you should illustrate the curve of x3+x+3x^3 + x + 3 on the interval (2,1)(-2, 1), ensuring that it passes through the x-axis, confirming the existence of the solution.

Summary:

  • f(x)f(x) is continuous on (2,1)(-2, 1).
  • f(2)=7f(-2) = -7, f(1)=5f(1) = 5, and 0 lies between -7 and 5.
  • Therefore, by the Intermediate Value Theorem, a solution exists in the interval (2,1)(-2, 1).

Would you like further details on this, or help with solving any part?

Here are five related questions to expand your understanding:

  1. How does the Intermediate Value Theorem work for non-polynomial functions?
  2. Can there be more than one solution in the interval (2,1)(-2, 1)?
  3. What other methods can be used to solve x3+x+3=0x^3 + x + 3 = 0 besides the IVT?
  4. How would the graph of x3+x+3x^3 + x + 3 look outside the interval (2,1)(-2, 1)?
  5. How do you verify the exact root found using graphing tools?

Tip: Always remember that polynomials are continuous everywhere, so the IVT can easily apply to any interval for polynomial functions!

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Math Problem Analysis

Mathematical Concepts

Continuity of Functions
Polynomials
Intermediate Value Theorem

Formulas

Polynomial formula: x^3 + x + 3

Theorems

Intermediate Value Theorem

Suitable Grade Level

College Level