Math Problem Statement

Use the given functions f(x) = √(3x - 2) and g(x) = 3x + 6 to find (f + g)(x), (f - g)(x), (f * g)(x), and (f / g)(x) along with their respective domains.

Solution

Let's start by analyzing the given functions and solving the operations:

We have:

  • f(x)=3x2f(x) = \sqrt{3x - 2}
  • g(x)=3x+6g(x) = 3x + 6

We are asked to find the following:

1. (f+g)(x)(f + g)(x)

This is simply the sum of f(x)f(x) and g(x)g(x): (f+g)(x)=f(x)+g(x)=3x2+(3x+6)(f + g)(x) = f(x) + g(x) = \sqrt{3x - 2} + (3x + 6)

Now, for the domain:

  • The function f(x)=3x2f(x) = \sqrt{3x - 2} requires 3x203x - 2 \geq 0, which gives: x23x \geq \frac{2}{3}
  • The function g(x)=3x+6g(x) = 3x + 6 has no restrictions on xx (its domain is (,)(-\infty, \infty)).

Therefore, the domain of (f+g)(x)(f + g)(x) is: D=[23,)D = \left[ \frac{2}{3}, \infty \right)


2. (fg)(x)(f - g)(x)

This is the difference between f(x)f(x) and g(x)g(x): (fg)(x)=f(x)g(x)=3x2(3x+6)(f - g)(x) = f(x) - g(x) = \sqrt{3x - 2} - (3x + 6)

For the domain, it is the same as for f(x)f(x): D=[23,)D = \left[ \frac{2}{3}, \infty \right)


3. (fg)(x)(f \cdot g)(x)

This is the product of f(x)f(x) and g(x)g(x): (fg)(x)=f(x)g(x)=3x2(3x+6)(fg)(x) = f(x) \cdot g(x) = \sqrt{3x - 2} \cdot (3x + 6)

For the domain, we again use the domain of f(x)f(x), since g(x)g(x) has no restrictions: D=[23,)D = \left[ \frac{2}{3}, \infty \right)


4. (fg)(x)\left( \frac{f}{g} \right)(x)

This is the quotient of f(x)f(x) and g(x)g(x): (fg)(x)=3x23x+6\left( \frac{f}{g} \right)(x) = \frac{\sqrt{3x - 2}}{3x + 6}

For the domain, two conditions must be met:

  1. 3x203x - 2 \geq 0 (so f(x)f(x) is defined), which gives x23x \geq \frac{2}{3}.
  2. 3x+603x + 6 \neq 0 (so the denominator is non-zero), which gives x2x \neq -2.

Thus, the domain is: D=[23,){2}D = \left[ \frac{2}{3}, \infty \right) \setminus \{-2\}


Summary:

  1. (f+g)(x)=3x2+3x+6(f + g)(x) = \sqrt{3x - 2} + 3x + 6
    • Domain: [23,)\left[ \frac{2}{3}, \infty \right)
  2. (fg)(x)=3x2(3x+6)(f - g)(x) = \sqrt{3x - 2} - (3x + 6)
    • Domain: [23,)\left[ \frac{2}{3}, \infty \right)
  3. (fg)(x)=3x2(3x+6)(fg)(x) = \sqrt{3x - 2} \cdot (3x + 6)
    • Domain: [23,)\left[ \frac{2}{3}, \infty \right)
  4. (fg)(x)=3x23x+6\left( \frac{f}{g} \right)(x) = \frac{\sqrt{3x - 2}}{3x + 6}
    • Domain: [23,){2}\left[ \frac{2}{3}, \infty \right) \setminus \{-2\}

Let me know if you'd like further clarifications or have any other questions!

Related Questions:

  1. How do we simplify radical functions like f(x)=3x2f(x) = \sqrt{3x - 2}?
  2. What are the general rules for finding the domain of radical functions?
  3. Why do we exclude x=2x = -2 from the domain of fg(x)\frac{f}{g}(x)?
  4. How do sum and difference of functions affect their domains?
  5. What happens if both functions have domain restrictions in a function operation?

Tip:

Always check for restrictions in both the numerator and denominator when dealing with quotient functions to avoid division by zero!

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Math Problem Analysis

Mathematical Concepts

Function Operations
Radical Functions
Domain of Functions

Formulas

(f + g)(x) = f(x) + g(x)
(f - g)(x) = f(x) - g(x)
(fg)(x) = f(x) * g(x)
(f / g)(x) = f(x) / g(x)

Theorems

For square root functions: the expression under the square root must be greater than or equal to zero.
For rational functions: the denominator must not equal zero.

Suitable Grade Level

Grades 9-12