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Reflection across x -axis: g ( x ) = – f (x) Reflection across y -axis: g(x) = f ( – x )

An absolute-value function is a function whose rule contains an absolute-value expression. The graph of the parent absolute-value function f ( x ) = | x | has a V shape with a minimum point or vertex at (0, 0).

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Reflection across x -axis: g ( x ) = – f (x) Reflection across y -axis: g(x) = f ( – x )

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  1. An absolute-value function is a function whose rule contains an absolute-value expression. The graph of the parent absolute-value function f(x) = |x| has a V shape with a minimum point or vertex at (0, 0). The absolute-value parent function is composed of two linear pieces, one with a slope of –1 and one with a slope of 1. In Lesson 2-6, you transformed linear functions. You can also transform absolute-value functions.

  2. Remember! Remember! Remember! Reflection across x-axis: g(x) = –f(x) Reflection across y-axis: g(x) = f(–x) Vertical stretch and compression : g(x) = af(x) Horizontal stretch and compression: g(x) = f The general forms for translations are Vertical: g(x) = f(x) + k Horizontal: g(x) = f(x– h)

  3. Ex 1A: Perform the transformation on f(x) = |x|. Then graph the transformed function g(x). 5 units down f(x) = |x| g(x) = f(x) + k The graph of g(x) = |x| – 5 is the graph of f(x) = |x| after a vertical shift of 5 units down. The vertex of g(x) is (0, –5). g(x) = |x| – 5 The graph of g(x) = |x|– 5 is the graph of f(x) = |x| after a vertical shift of 5 units down. The vertex of g(x) is (0, –5). f(x) g(x)

  4. Ex 1B: Perform the transformation on f(x) = |x|. Then graph the transformed function g(x). 1 unit left f(x) = |x| g(x) = f(x– h) g(x) = |x – (–1)| = |x + 1| The graph of g(x) = |x + 1| is the graph of f(x) = |x| after a horizontal shift of 1 unit left. The vertex of g(x) is (–1, 0). f(x) g(x)

  5. Because the entire graph moves when shifted, the shift from f(x) = |x| determines the vertex of an absolute-value graph. Ex 2: Translate f(x) = |x|so that the vertex is at (–1, –3). Then graph. g(x) = |x – h| + k g(x) = |x – (–1)| + (–3) f(x) g(x) = |x + 1| – 3 The graph of g(x) = |x + 1| – 3 is the graph of f(x) = |x| after a vertical shift down 3 units and a horizontal shift left 1 unit. g(x) The graph confirms that the vertex is (–1, –3).

  6. g f Ex 3A: Perform the transformation. Then graph. Reflect the graph. f(x) =|x –2| + 3 across the y-axis. Take the opposite of the input value. g(x) = f(–x) g(x) = |(–x) – 2| + 3 The vertex of the graph g(x) = |–x – 2| + 3 is (–2, 3).

  7. f(x) g(x) Ex 3B: Stretch the graph. f(x) = |x| – 1 vertically by a factor of 2. g(x) = af(x) g(x) = 2(|x| – 1) Multiply the entire function by 2. g(x) = 2|x| – 2 The graph of g(x) = 2|x| – 2 is the graph of f(x) = |x| – 1 after a vertical stretch by a factor of 2. The vertex of g is at (0, –2).

  8. g Substitute for b. Compress the graph of f(x) = |x + 2| – 1 horizontally by a factor of . Ex 3C: Simplify. g(x) = |2x + 2| – 1 The graph of g(x) = |2x + 2|– 1 is the graph of f(x) = |x + 2| – 1 after a horizontal compression by a factor of . The vertex of g is at (–1, –1). f

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