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Ch. 4 - Exponential and Logarithmic Functions
Blitzer - College Algebra 8th Edition
Blitzer8th EditionCollege AlgebraISBN: 9780136970514Not the one you use?Change textbook
Chapter 5, Problem 30

Graph f(x) = 2^x and g(x) = log2 x in the same rectangular coordinate system. Use the graphs to determine each function's domain and range.

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Understand the functions: f(x) = 2^x is an exponential function with base 2, and g(x) = log₂(x) is a logarithmic function with base 2. These two functions are inverses of each other.
Graph f(x) = 2^x: Start by creating a table of values for x and f(x). For example, calculate f(x) for x = -2, -1, 0, 1, and 2. Plot these points on the coordinate plane and draw a smooth curve passing through them. Note that the graph will pass through (0, 1) and approach the x-axis as x approaches negative infinity, but it will never touch the x-axis.
Graph g(x) = log₂(x): Create a table of values for x and g(x). For example, calculate g(x) for x = 1/4, 1/2, 1, 2, and 4. Plot these points on the coordinate plane and draw a smooth curve passing through them. Note that the graph will pass through (1, 0) and approach the y-axis as x approaches 0 from the right, but it will never touch the y-axis.
Determine the domain and range of f(x): The domain of f(x) = 2^x is all real numbers (-∞, ∞), because you can raise 2 to any real number power. The range is (0, ∞), because the output of 2^x is always positive.
Determine the domain and range of g(x): The domain of g(x) = log₂(x) is (0, ∞), because you can only take the logarithm of positive numbers. The range is all real numbers (-∞, ∞), because the logarithmic function can produce any real number as an output.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Exponential Functions

Exponential functions, such as f(x) = 2^x, are mathematical expressions where a constant base is raised to a variable exponent. These functions exhibit rapid growth as x increases and approach zero as x decreases. The domain of an exponential function is all real numbers, while the range is limited to positive values, indicating that the output never reaches zero.
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Logarithmic Functions

Logarithmic functions, like g(x) = log2 x, are the inverses of exponential functions. They answer the question of what exponent a base must be raised to in order to produce a given number. The domain of a logarithmic function is restricted to positive real numbers, while the range encompasses all real numbers, reflecting that logarithms can yield any real value.
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Graphs of Logarithmic Functions

Graphing Functions

Graphing functions involves plotting points on a coordinate system to visualize their behavior. For f(x) = 2^x, the graph will show exponential growth, while g(x) = log2 x will illustrate a gradual increase that approaches infinity. Understanding how to graph these functions helps in determining their domains and ranges, as well as their intersections and asymptotic behavior.
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