24. Suppose that \( f(x)-\log _{3}(2 x+1)-2 \), a. What is the domain of \( f(x) \) ? Explain how you determined your answer. b. Determine the value of \( f(13) \). What point is on the graph of \( f(x) \) ? c. Find the zero(s) of \( f(x) \)
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The domain of \( f(x) = \log_{3}(2x + 1) + 2 \) is determined by the argument of the logarithm, which must be greater than zero. Thus, \( 2x + 1 > 0 \), leading to \( x > -\frac{1}{2} \). Therefore, the domain of \( f(x) \) is \( x \in \left(-\frac{1}{2}, \infty\right) \). To determine \( f(13) \), substitute \( x = 13 \) into the function: \( f(13) = \log_{3}(2 \cdot 13 + 1) + 2 = \log_{3}(27) + 2 = 3 + 2 = 5 \). Thus, the point \( (13, 5) \) lies on the graph of \( f(x) \). To find the zero(s) of \( f(x) \), we set \( f(x) = 0 \): \[ \log_{3}(2x + 1) + 2 = 0 \implies \log_{3}(2x + 1) = -2. \] This means \( 2x + 1 = 3^{-2} = \frac{1}{9} \), which rearranges to \( 2x = \frac{1}{9} - 1 = -\frac{8}{9} \) giving \( x = -\frac{4}{9} \). The zero of \( f(x) \) is at \( x = -\frac{4}{9} \).