Math Problem Statement

Let f : R → R. Find the domain and range of the following functions: (i) 5 9−x2

Solution

Given the function f(x)=59x2f(x) = \frac{5}{9 - x^2}, we are tasked with finding its domain and range.

1. Domain:

The domain of a function consists of all real values of xx for which the function is defined. For rational functions (functions that have a denominator), the function is undefined wherever the denominator is zero.

Here, the denominator is 9x29 - x^2. So, we set: 9x209 - x^2 \neq 0 This implies: x29x^2 \neq 9 Taking square roots on both sides: x3andx3x \neq 3 \quad \text{and} \quad x \neq -3 Thus, the function is undefined at x=3x = 3 and x=3x = -3.

So, the domain is: (,3)(3,3)(3,)\boxed{(-\infty, -3) \cup (-3, 3) \cup (3, \infty)}

2. Range:

The range of a function consists of all possible output values (or yy-values) of the function.

To find the range, we consider the form of the function: f(x)=59x2f(x) = \frac{5}{9 - x^2}

Since the denominator 9x29 - x^2 cannot be zero, 9x29 - x^2 must be either positive or negative but never zero. The denominator decreases as x2x^2 increases, and the function's behavior changes accordingly.

Key points:

  • As x29x^2 \to 9 (as xx approaches 3 or -3), the denominator 9x209 - x^2 \to 0, making the function tend toward infinity.
  • As x2x^2 becomes very large (far from 3 and -3), the denominator becomes more negative, and the overall function tends towards zero but is always negative for large x2x^2.

Thus, the range of f(x)f(x) is: (,0)(0,)\boxed{(-\infty, 0) \cup (0, \infty)} (Note that 00 is excluded because the function never actually reaches 00.)


Would you like a detailed breakdown of how the range is derived or have any other questions?

Related questions:

  1. How do you find the domain of a square root function?
  2. What is the domain of f(x)=1x2f(x) = \frac{1}{x - 2}?
  3. How do asymptotes affect the range of rational functions?
  4. Can a function have a domain that excludes more than two points?
  5. How would the range change if the numerator in this function were different?

Tip: When determining the domain of rational functions, always check where the denominator is zero—these are points of discontinuity.

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Math Problem Analysis

Mathematical Concepts

Rational Functions
Domain and Range
Discontinuities

Formulas

f(x) = 5 / (9 − x^2)
x^2 ≠ 9

Theorems

The concept of domain excludes points where the denominator is zero.
Range is determined based on asymptotic behavior.

Suitable Grade Level

Grades 10-12