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Graph the function below by moving the key points. \[ f(x)=2 \log _{3}(x) \]

Ask by Deleon Coleman. in the United States
Feb 12,2025

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Answer

To graph \( f(x) = 2 \log_{3}(x) \), start with the basic logarithm \( g(x) = \log_{3}(x) \). Then, stretch the graph vertically by a factor of 2. Key points move as follows: - (1, 0) stays the same. - (3, 1) becomes (3, 2). - (1/3, –1) becomes (1/3, –2). Draw a vertical asymptote at x = 0, plot these points, and sketch a smooth curve that approaches –∞ as x approaches 0 and increases slowly as x increases.

Solution

We want to graph   f(x) = 2·log₃(x) by “moving” key points. One good strategy is to start with the basic logarithm function g(x) = log₃(x) and then apply the transformation that multiplies the output by 2 (a vertical stretch). Step 1. Identify the basic graph of g(x) = log₃(x):  • Domain: x > 0.  • Vertical asymptote at x = 0.  • The point (1, 0) is on the graph because log₃(1) = 0.  • Other easy-to-calculate points:   – When x = 3, log₃(3) = 1, so the point (3, 1) is on g(x).   – When x = 1/3, log₃(1/3) = –1, so (1/3, –1) is on g(x). Step 2. Apply the transformation f(x) = 2·log₃(x)  • This multiplies all y-values by 2. In other words, we “stretch” the graph vertically by a factor of 2.  • The new key points become:   – (1, 0) stays the same because 2·0 = 0.   – (3, 1) moves to (3, 2) because 2·1 = 2.   – (1/3, –1) moves to (1/3, –2) because 2·(–1) = –2. Step 3. Describe the new graph:  • Domain: Still x > 0.  • Vertical asymptote: Still the line x = 0.  • Behavior:   – As x → 0⁺, f(x) → –∞.   – f(1) = 2·log₃(1) = 0.   – As x increases further, f(x) increases but slowly (logarithmic growth); for instance, f(9) = 2·log₃(9) = 2·2 = 4.  • The graph curves upward slowly, with the same “shape” as log₃(x) but with values doubled. Step 4. Sketching the graph:  1. Draw a vertical dashed line at x = 0 to indicate the asymptote.  2. Plot the key points:   – (1, 0)   – (3, 2)   – (1/3, –2)  3. Sketch a smooth curve passing through these points that approaches –∞ as x → 0⁺ and rises gradually as x increases. Your final graph of f(x) = 2·log₃(x) shows a logarithmic curve with a vertical stretch relative to the basic log₃(x) graph.

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To graph the function \( f(x) = 2 \log_{3}(x) \), start by identifying key points for the logarithmic function \( \log_{3}(x) \). Remember, the logarithmic graph passes through the point \( (1, 0) \) because \( \log_{3}(1) = 0 \). Next, when \( x = 3 \), \( \log_{3}(3) = 1 \), so that gives us the point \( (3, 1) \). Since the function is multiplied by 2, these points become \( (1, 0) \) and \( (3, 2) \). Lastly, the vertical asymptote at \( x = 0 \) remains, as logarithmic functions never touch the y-axis. Your graph will now show a curve that approaches the y-axis, goes through (1, 0), and accelerates through (3, 2). For an additional boost, remember that the domain of this function is \( x > 0 \) since logs can't take non-positive numbers. This means your graph starts at the y-axis and swoops rightwards. And, don’t forget about the range! The output can go infinitely positive or negative, giving you a complete view of how the logarithmic function behaves.

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