Questions: For the given functions, find (f ∘ g)(x) and (g ∘ f)(x) and the domain of each. f(x) = 3 / (1 - 7x), g(x) = 1 / x

For the given functions, find (f ∘ g)(x) and (g ∘ f)(x) and the domain of each.  
f(x) = 3 / (1 - 7x), g(x) = 1 / x
Transcript text: For the given functions, find $(f \circ g)(x)$ and $(g \circ f)(x)$ and the domain of each. \[ f(x)=\frac{3}{1-7 x}, g(x)=\frac{1}{x} \]
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Solution

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Find \((g \circ f)(x)\)

Substitute \(f(x)\) into \(g(x)\)

To find \((g \circ f)(x)\), substitute \(f(x) = \frac{3}{1-7x}\) into \(g(x) = \frac{1}{x}\). This gives us: \[ g(f(x)) = g\left(\frac{3}{1-7x}\right) = \frac{1}{\frac{3}{1-7x}} \]

Simplify the expression

Simplify \(\frac{1}{\frac{3}{1-7x}}\) to get: \[ \frac{1-7x}{3} \]

\(\boxed{(g \circ f)(x) = \frac{1-7x}{3}}\)

Find the domain of \((f \circ g)(x)\)

Identify where the denominator is zero

The function \((f \circ g)(x) = \frac{3x}{x-7}\) has a denominator of \(x-7\). Set the denominator not equal to zero: \[ x-7 \neq 0 \implies x \neq 7 \]

State the domain

The domain of \((f \circ g)(x)\) is all real numbers except 7: \[ (-\infty, 7) \cup (7, \infty) \]

\(\boxed{\text{Domain of } (f \circ g)(x): (-\infty, 7) \cup (7, \infty)}\)

Find the domain of \((g \circ f)(x)\)

Consider the domain of the inner function \(f(x)\)

The function \(f(x) = \frac{3}{1-7x}\) has a denominator of \(1-7x\). Set the denominator not equal to zero: \[ 1-7x \neq 0 \implies x \neq \frac{1}{7} \]

State the domain

The domain of \((g \circ f)(x)\) is all real numbers except \(\frac{1}{7}\): \[ (-\infty, \frac{1}{7}) \cup (\frac{1}{7}, \infty) \]

\(\boxed{\text{Domain of } (g \circ f)(x): (-\infty, \frac{1}{7}) \cup (\frac{1}{7}, \infty)}\)

\((g \circ f)(x) = \frac{1-7x}{3}\)
Domain of \((f \circ g)(x): (-\infty, 7) \cup (7, \infty)\)
Domain of \((g \circ f)(x): (-\infty, \frac{1}{7}) \cup (\frac{1}{7}, \infty)\)

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