Math Problem Statement

Suppose that the functions f and g are defined as follows: f(x) = x - 3 and g(x) = √(3x - 4). Find f/g and f - g. Then, give their domains using interval notation.

Solution

We are given two functions, f(x)=x3f(x) = x - 3 and g(x)=3x4g(x) = \sqrt{3x - 4}, and we need to find:

  1. The function fg\frac{f}{g}
  2. The function fgf - g

Additionally, we need to determine the domain of each resulting function using interval notation.

1. Finding fg\frac{f}{g}:

fg(x)=x33x4\frac{f}{g}(x) = \frac{x - 3}{\sqrt{3x - 4}}

Domain of fg\frac{f}{g}:

For the domain of fg\frac{f}{g}, we need to consider two things:

  • The square root function 3x4\sqrt{3x - 4} requires that 3x403x - 4 \geq 0, so: 3x4    x433x \geq 4 \implies x \geq \frac{4}{3}
  • Additionally, since g(x)=3x4g(x) = \sqrt{3x - 4} is in the denominator, we must ensure that g(x)0g(x) \neq 0. Therefore: 3x40    3x40    x43\sqrt{3x - 4} \neq 0 \implies 3x - 4 \neq 0 \implies x \neq \frac{4}{3} Thus, the domain of fg\frac{f}{g} is (43,)\left( \frac{4}{3}, \infty \right).

2. Finding fgf - g:

fg(x)=(x3)3x4f - g(x) = (x - 3) - \sqrt{3x - 4}

Domain of fgf - g:

For the domain of fgf - g, we only need to ensure that the square root 3x4\sqrt{3x - 4} is defined, which means: 3x40    x433x - 4 \geq 0 \implies x \geq \frac{4}{3} So, the domain of fgf - g is [43,)\left[ \frac{4}{3}, \infty \right).

Final Results:

  1. The function fg(x)=x33x4\frac{f}{g}(x) = \frac{x - 3}{\sqrt{3x - 4}} has a domain of (43,)\left( \frac{4}{3}, \infty \right).
  2. The function fg(x)=(x3)3x4f - g(x) = (x - 3) - \sqrt{3x - 4} has a domain of [43,)\left[ \frac{4}{3}, \infty \right).

Would you like more details on the steps? Here are some related questions:

  1. What happens if g(x)g(x) equals zero in more general cases?
  2. How do you simplify rational expressions like fg\frac{f}{g}?
  3. Can fg(x)f - g(x) ever be negative? Why or why not?
  4. What are the general rules for finding domains when square roots are involved?
  5. How does the difference in domain intervals between fg\frac{f}{g} and fgf - g affect their graphs?

Tip: Always check for restrictions like square roots and denominators when determining domains.

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Math Problem Analysis

Mathematical Concepts

Algebra
Functions
Domains
Square Roots
Rational Expressions

Formulas

f(x) = x - 3
g(x) = √(3x - 4)
(f/g)(x) = (x - 3) / √(3x - 4)
(f - g)(x) = (x - 3) - √(3x - 4)

Theorems

To determine the domain of a function with a square root, set the expression inside the square root to be greater than or equal to zero: 3x - 4 ≥ 0.
To find the domain of a rational function, ensure the denominator is not zero: √(3x - 4) ≠ 0.

Suitable Grade Level

Grades 10-12