Find the domain of each logarithmic function. f(x) = log₅(x+4)

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Recall that the domain of a logarithmic function \( f(x) = \log_b(g(x)) \) consists of all values of \( x \) for which the argument \( g(x) \) is positive, because the logarithm of zero or a negative number is undefined.

Identify the argument of the logarithm in the given function: \( f(x) = \log_5(x+4) \). Here, the argument is \( x + 4 \).

Set up the inequality to find where the argument is positive: \( x + 4 > 0 \).

Solve the inequality for \( x \): subtract 4 from both sides to get \( x > -4 \).

Conclude that the domain of \( f(x) = \log_5(x+4) \) is all real numbers \( x \) such that \( x > -4 \).

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주요 개념

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Domain of a Function

The domain of a function is the set of all input values (x-values) for which the function is defined. For logarithmic functions, the domain is restricted because the argument inside the log must be positive. Identifying the domain involves finding all x-values that make the expression inside the logarithm greater than zero.

Properties of Logarithmic Functions

A logarithmic function log_b(x) is defined only for positive arguments x > 0, where b is the base and b > 0, b ≠ 1. This means the expression inside the log must be strictly greater than zero to avoid undefined values or complex numbers.

Inequalities and Solving for Domain

To find the domain of f(x) = log_5(x+4), solve the inequality x + 4 > 0. This involves basic algebraic manipulation to isolate x, resulting in the domain expressed as an interval. Understanding how to solve inequalities is essential for determining valid input values.

Find the domain of each logarithmic function. f(x) = log5(x+4)