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Ch. 2 - Graphs and Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 3, Problem 22

Graph each piecewise-defined function.
f(x)={6xif x33if x>3f(x) =\(\begin{cases}\)6 - x & \(\text{if }\) x \(\leq\) 3 \\3 & \(\text{if }\) x > 3\(\end{cases}\)

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Step 1: Understand the piecewise function definition. The function is defined as \(f(x) = -x - 2\) when \(x \leq 2\), and \(f(x) = -4\) when \(x > 2\). This means the graph will have two parts: one for \(x\) values less than or equal to 2, and another for \(x\) values greater than 2.
Step 2: Graph the first piece \(f(x) = -x - 2\) for \(x \leq 2\). This is a linear function with slope \(-1\) and y-intercept \(-2\). Plot points for values of \(x\) less than or equal to 2, for example at \(x=0\), \(f(0) = -0 - 2 = -2\), and at \(x=2\), \(f(2) = -2 - 2 = -4\). Connect these points with a straight line extending to the left.
Step 3: Graph the second piece \(f(x) = -4\) for \(x > 2\). This is a constant function, so for all \(x\) values greater than 2, the function value is \(-4\). Draw a horizontal line at \(y = -4\) starting just to the right of \(x=2\).
Step 4: Determine the type of points at \(x=2\). Since the first piece includes \(x=2\) (because of \(\leq\)), plot a solid dot at \((2, -4)\) on the line \(f(x) = -x - 2\). For the second piece, since it is defined for \(x > 2\), do not include the point at \(x=2\) on the constant line; instead, use an open circle at \((2, -4)\) to indicate that this point is not included in the second piece.
Step 5: Review the graph to ensure continuity and correct representation of the piecewise function. The graph should show a line with negative slope up to and including \(x=2\), and a horizontal line at \(y=-4\) for \(x\) values greater than 2, with the appropriate solid and open points at \(x=2\).

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Key Concepts

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

Piecewise-Defined Functions

A piecewise-defined function is a function composed of different expressions depending on the input value's domain. Each piece applies to a specific interval, and the function's overall graph is formed by combining these pieces. Understanding how to interpret and graph each piece separately is essential.
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Domain Restrictions of Composed Functions

Graphing Linear Functions

Graphing linear functions involves plotting points that satisfy the equation and connecting them with a straight line. For the piece where f(x) = -x - 2, this is a linear function with slope -1 and y-intercept -2, which helps in sketching the graph for x ≤ 2.
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Graphs of Logarithmic Functions

Domain Restrictions and Continuity

Domain restrictions specify where each piece of the function applies, affecting the graph's shape and endpoints. Understanding open and closed endpoints at boundary points (like x=2) is crucial to correctly represent the function's continuity or discontinuity.
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Domain Restrictions of Composed Functions