Math Problem Statement

Consider the function: f : R --> R defined by f(x) = x^2 + 1. The domain of f is restricted to (-2,4). Find the range

Solution

We are given the function f(x)=x2+1f(x) = x^2 + 1 and its domain is restricted to (2,4)(-2, 4), meaning the function is defined for all xx in the interval (2,4)(-2, 4). We need to find the range of this function on this restricted domain.

Steps to find the range:

  1. Analyze the function: The function is f(x)=x2+1f(x) = x^2 + 1, which is a parabola opening upwards. The value of f(x)f(x) depends on the value of x2x^2.

  2. Determine the behavior of the function on the domain: The domain is (2,4)(-2, 4), so we evaluate the function at the endpoints of this interval.

    • When x=2x = -2, f(2)=(2)2+1=4+1=5f(-2) = (-2)^2 + 1 = 4 + 1 = 5.
    • When x=4x = 4, f(4)=(4)2+1=16+1=17f(4) = (4)^2 + 1 = 16 + 1 = 17.

    Since the function f(x)=x2+1f(x) = x^2 + 1 is increasing in the interval [0,)[0, \infty) and decreasing in the interval (,0](-\infty, 0], we expect the minimum value to occur at the endpoints or near the vertex.

  3. Find the minimum and maximum values of the function:

    • The function is symmetric, so it achieves a minimum value at x=0x = 0, which is the midpoint of the interval (2,4)(-2, 4).
    • At x=0x = 0, f(0)=02+1=1f(0) = 0^2 + 1 = 1.
  4. Range of the function: Since f(x)f(x) increases from f(0)=1f(0) = 1 to f(4)=17f(4) = 17, and decreases from f(0)=1f(0) = 1 to f(2)=5f(-2) = 5, the range of ff on (2,4)(-2, 4) is the interval:

    [1,17)[1, 17)

Conclusion:

The range of the function f(x)=x2+1f(x) = x^2 + 1 when the domain is restricted to (2,4)(-2, 4) is [1,17)[1, 17).


Would you like a more detailed explanation of any of the steps? Here are 5 related questions to explore further:

  1. How would the range change if the domain was [2,4][-2, 4] instead of (2,4)(-2, 4)?
  2. What happens to the range if the function was f(x)=x21f(x) = x^2 - 1?
  3. How would you find the range of the function if the domain was restricted to a different interval?
  4. How can we determine whether a function is increasing or decreasing in an interval?
  5. What is the vertex of the function f(x)=x2+1f(x) = x^2 + 1, and how does it relate to the range?

Tip: Always check the endpoints and critical points when working with restricted domains to ensure you've covered all potential maximum and minimum values!

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Math Problem Analysis

Mathematical Concepts

Functions
Quadratic Functions
Domain and Range

Formulas

f(x) = x^2 + 1

Theorems

Range of a function
Behavior of quadratic functions

Suitable Grade Level

Grades 9-11