Answer
(a) \( (f-g)(x) = \frac{x^2 - 8x + 2}{(x-4)(x-6)} \), Domain: All real numbers except \( x = 4 \) and \( x = 6 \).
(b) \( \left(\frac{g}{f}\right)(x) = \frac{5(x-4)}{(x-6)(x+3)} \), Domain: All real numbers except \( x = 6 \) and \( x = -3 \).
Solution
To solve the problem, we will find the new functions \( (f-g)(x) \) and \( \left(\frac{g}{f}\right)(x) \) step by step, simplifying the results and describing their domains.
### Given Functions
- \( f(x) = \frac{x+3}{x-4} \)
- \( g(x) = \frac{5}{x-6} \)
### (a) Finding \( (f-g)(x) \)
The function \( (f-g)(x) \) is defined as:
\[
(f-g)(x) = f(x) - g(x) = \frac{x+3}{x-4} - \frac{5}{x-6}
\]
To subtract these fractions, we need a common denominator, which is \( (x-4)(x-6) \). Thus, we rewrite the fractions:
\[
(f-g)(x) = \frac{(x+3)(x-6) - 5(x-4)}{(x-4)(x-6)}
\]
Now, we will expand the numerator:
1. Expand \( (x+3)(x-6) \):
\[
(x+3)(x-6) = x^2 - 6x + 3x - 18 = x^2 - 3x - 18
\]
2. Expand \( 5(x-4) \):
\[
5(x-4) = 5x - 20
\]
Now, substitute these back into the numerator:
\[
(f-g)(x) = \frac{x^2 - 3x - 18 - (5x - 20)}{(x-4)(x-6)} = \frac{x^2 - 3x - 18 - 5x + 20}{(x-4)(x-6)}
\]
Combine like terms in the numerator:
\[
= \frac{x^2 - 8x + 2}{(x-4)(x-6)}
\]
### Domain of \( (f-g)(x) \)
The domain of \( (f-g)(x) \) is determined by the values that make the denominator zero. The denominator is zero when:
1. \( x - 4 = 0 \) → \( x = 4 \)
2. \( x - 6 = 0 \) → \( x = 6 \)
Thus, the domain of \( (f-g)(x) \) is all real numbers except \( x = 4 \) and \( x = 6 \).
### (b) Finding \( \left(\frac{g}{f}\right)(x) \)
The function \( \left(\frac{g}{f}\right)(x) \) is defined as:
\[
\left(\frac{g}{f}\right)(x) = \frac{g(x)}{f(x)} = \frac{\frac{5}{x-6}}{\frac{x+3}{x-4}} = \frac{5}{x-6} \cdot \frac{x-4}{x+3}
\]
This simplifies to:
\[
\left(\frac{g}{f}\right)(x) = \frac{5(x-4)}{(x-6)(x+3)}
\]
### Domain of \( \left(\frac{g}{f}\right)(x) \)
The domain of \( \left(\frac{g}{f}\right)(x) \) is determined by the values that make the denominators zero. The denominators are zero when:
1. \( x - 6 = 0 \) → \( x = 6 \)
2. \( x + 3 = 0 \) → \( x = -3 \)
Thus, the domain of \( \left(\frac{g}{f}\right)(x) \) is all real numbers except \( x = 6 \) and \( x = -3 \).
### Summary of Results
(a)
\[
(f-g)(x) = \frac{x^2 - 8x + 2}{(x-4)(x-6)}, \quad \text{Domain: } x \in \mathbb{R}, x \neq 4, 6
\]
(b)
\[
\left(\frac{g}{f}\right)(x) = \frac{5(x-4)}{(x-6)(x+3)}, \quad \text{Domain: } x \in \mathbb{R}, x \neq 6, -3
\]
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