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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 57

Graph f and g in the same rectangular coordinate system. Then find the point of intersection of the two graphs. f(x) = 2x, g(x) = 2-x

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First, understand the functions given: \(f(x) = 2^x\) is an exponential growth function, and \(g(x) = 2^{-x}\) is an exponential decay function. Both are defined for all real numbers \(x\).
To graph both functions on the same coordinate system, create a table of values for each function by choosing several \(x\) values (for example, \(-2, -1, 0, 1, 2\)) and calculating the corresponding \(f(x)\) and \(g(x)\) values.
Plot the points from the tables for \(f(x)\) and \(g(x)\) on the coordinate plane. Remember that \(f(x) = 2^x\) increases as \(x\) increases, while \(g(x) = 2^{-x}\) decreases as \(x\) increases.
To find the point of intersection algebraically, set the two functions equal to each other: \(2^x = 2^{-x}\). This equation will help find the \(x\)-value(s) where the graphs intersect.
Solve the equation \(2^x = 2^{-x}\) by using properties of exponents. For example, rewrite \(2^{-x}\) as \(\frac{1}{2^x}\) and solve for \(x\). Once you find \(x\), substitute it back into either \(f(x)\) or \(g(x)\) to find the corresponding \(y\)-coordinate of the intersection point.

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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 have the form f(x) = a^x, where the base a is a positive constant. They model rapid growth or decay depending on whether the exponent is positive or negative. Understanding their shape and behavior is essential for graphing and analyzing functions like f(x) = 2^x and g(x) = 2^-x.
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Exponential Functions

Graphing Functions on the Coordinate Plane

Graphing involves plotting points (x, f(x)) on the rectangular coordinate system to visualize the function's behavior. Comparing two graphs on the same axes helps identify intersections and relative positions. Accurate plotting of exponential functions reveals their growth and decay patterns.
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Finding Points of Intersection

The point of intersection of two graphs is where their function values are equal, i.e., f(x) = g(x). Solving this equation algebraically or by inspection gives the x-coordinate(s) of intersection. Substituting back finds the corresponding y-coordinate(s), providing the exact intersection point(s).
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Related Practice
Textbook Question

Solve each logarithmic equation in Exercises 49–92. Be sure to reject any value of x that is not in the domain of the original logarithmic expressions. Give the exact answer. Then, where necessary, use a calculator to obtain a decimal approximation, correct to two decimal places, for the solution. log3(x+4)=−3

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Textbook Question

In Exercises 53-58, begin by graphing f(x) = log₂ x. Then use transformations of this graph to graph the given function. What is the vertical asymptote? Use the graphs to determine each function's domain and range. g(x) = (1/2)log₂ x

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Textbook Question

Use properties of logarithms to condense each logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. Where possible, evaluate logarithmic expressions without using a calculator. 5 ln x - 2 ln y

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Textbook Question

Use properties of logarithms to condense each logarithmic expression. Write the expression as a single logarithm whose coefficient is 1. (1/2)ln x - ln y

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Textbook Question

Begin by graphing f(x) = log₂ x. Then use transformations of this graph to graph the given function. What is the vertical asymptote? Use the graphs to determine each function's domain and range. h(x) = 2 + log2x

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Textbook Question

Begin by graphing f(x) = log₂ x. Then use transformations of this graph to graph the given function. What is the vertical asymptote? Use the graphs to determine each function's domain and range. h(x)=1+ log₂ x

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