Math Problem Statement

In Exercises 3 and 4, find the domains and ranges of f, g, f/g, and g/f. For Exercise 5, if f(x) = x + 5 and g(x) = x^2 − 3, find the following: a) f(g(0)), b) g(f(0)), c) f(g(x)), and d) g(f(x)).

Solution

Let’s break this down!

Exercises 3 & 4: Domains and Ranges
3. f(x)=2f(x) = 2, g(x)=x2+1g(x) = x^2 + 1:

  • f(x)=2f(x) = 2:

    • Domain: All real numbers (R\mathbb{R}), as it’s constant.
    • Range: {2}\{2\}, since f(x)f(x) always equals 2.
  • g(x)=x2+1g(x) = x^2 + 1:

    • Domain: R\mathbb{R} (polynomial function).
    • Range: [1,)[1, \infty), since x20x^2 \geq 0.
  • fg=2x2+1\frac{f}{g} = \frac{2}{x^2 + 1}:

    • Domain: R\mathbb{R}, because g(x)0g(x) \neq 0.
    • Range: (0,2](0, 2], since 2x2+12\frac{2}{x^2 + 1} \leq 2.
  1. f(x)=1f(x) = 1, g(x)=1+xg(x) = 1 + \sqrt{x}:
    • f(x)=1f(x) = 1:

      • Domain: R\mathbb{R}.
      • Range: {1}\{1\}.
    • g(x)=1+xg(x) = 1 + \sqrt{x}:

      • Domain: [0,)[0, \infty) (since x\sqrt{x} is defined for non-negative xx).
      • Range: [1,)[1, \infty), since x0\sqrt{x} \geq 0.
    • fg=11+x\frac{f}{g} = \frac{1}{1 + \sqrt{x}}:

      • Domain: [0,)[0, \infty).
      • Range: (0,1](0, 1], since 1+x11 + \sqrt{x} \geq 1.

Exercise 5: Composites
Given f(x)=x+5f(x) = x + 5 and g(x)=x23g(x) = x^2 - 3:
a. f(g(0))f(g(0)):

  • g(0)=023=3g(0) = 0^2 - 3 = -3.
  • f(3)=3+5=2f(-3) = -3 + 5 = 2.
  • Answer: 22.

b. g(f(0))g(f(0)):

  • f(0)=0+5=5f(0) = 0 + 5 = 5.
  • g(5)=523=253=22g(5) = 5^2 - 3 = 25 - 3 = 22.
  • Answer: 2222.

c. f(g(x))f(g(x)):

  • g(x)=x23g(x) = x^2 - 3.
  • f(g(x))=f(x23)=(x23)+5=x2+2f(g(x)) = f(x^2 - 3) = (x^2 - 3) + 5 = x^2 + 2.
  • Answer: x2+2x^2 + 2.

d. g(f(x))g(f(x)):

  • f(x)=x+5f(x) = x + 5.
  • g(f(x))=g(x+5)=(x+5)23=x2+10x+253=x2+10x+22g(f(x)) = g(x + 5) = (x + 5)^2 - 3 = x^2 + 10x + 25 - 3 = x^2 + 10x + 22.
  • Answer: x2+10x+22x^2 + 10x + 22.

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5 Related Questions:

  1. How do you find the domain of a square root function like g(x)=1+xg(x) = 1 + \sqrt{x}?
  2. What is the relationship between composite functions and their domains?
  3. How does a constant function’s range differ from that of a polynomial?
  4. How do you determine the range of a fraction function like fg\frac{f}{g}?
  5. What happens if a composite function results in an undefined value?

Tip: Always verify the domain of inner and outer functions when working with compositions!

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Math Problem Analysis

Mathematical Concepts

Functions
Domain and Range
Composite Functions
Rational Functions

Formulas

Domain of a square root function: x ≥ 0
Domain of rational functions: Exclude values making the denominator zero
Composite functions: f(g(x)) and g(f(x))

Theorems

Square root properties
Range analysis using inequalities

Suitable Grade Level

Grades 10-12