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Ch. 2 - Graphs and Functions
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063당신이 사용하는 게 아니라요?교과서 변경
3장, 문제 41

Give a rule for each piecewise-defined function. Also give the domain and range.
Graph of a piecewise function with arrows and points showing domain and range on x and y axes.

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Step 1: Identify the different pieces of the piecewise function by looking at the graph and noting where the function changes its rule. Here, the graph has two distinct parts: one for x-values less than or equal to -1, and another for x-values greater than -1.
Step 2: For the first piece (x ≤ -1), observe the graph's behavior. The graph is a horizontal line at y = -2 from x = -8 to x = -1, including the point (-1, -2) (solid dot). So, the rule for this piece is \(f(x) = -2\) for \(x \leq -1\).
Step 3: For the second piece (x > -1), the graph shows a curve starting just after x = -1 (open circle at (-1, 0)) and increasing through points like (1, 2) and (2, 3). This looks like a quadratic function. The curve resembles \(f(x) = x^2\) shifted down by 1 unit, so the rule is \(f(x) = x^2 - 1\) for \(x > -1\).
Step 4: Write the piecewise function combining both parts: \[ f(x) = \begin{cases} -2 & \text{if } x \leq -1 \\ x^2 - 1 & \text{if } x > -1 \end{cases} \]
Step 5: Determine the domain and range. The domain is all x-values covered by the graph, which is from -8 to 2 (including -8 and 2). The range is the set of y-values the function takes: from -2 (lowest value on the horizontal line) up to 3 (highest point on the curve). So, domain: \([-8, 2]\), range: \([-2, 3]\).

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Piecewise-Defined Functions

A piecewise-defined function is a function composed of multiple sub-functions, each applying to a specific interval of the domain. Understanding how to write the rule for each piece involves identifying the function's behavior on different parts of the x-axis and expressing each part with its own formula.
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Domain Restrictions of Composed Functions

Domain and Range

The domain of a function is the set of all possible input values (x-values), while the range is the set of all possible output values (y-values). For piecewise functions, the domain is often split into intervals, and the range is determined by the outputs of each piece.
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4:22
Domain & Range of Transformed Functions

Interpreting Graphs with Open and Closed Points

Graphs of piecewise functions often use open circles to indicate that a point is not included in the function (excluded endpoint) and closed circles to show inclusion. Recognizing these helps determine the exact domain intervals and whether endpoints are included or excluded.
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Graphing Equations of Two Variables by Plotting Points