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Vertical Stretching or Shrinking of the Graph of a Function

Vertical Stretching or Shrinking of the Graph of a Function. Suppose that a > 0. If a point ( x , y ) lies on the graph of y = ( x ), then the point ( x , ay ) lies on the graph of y = a ( x ).

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Vertical Stretching or Shrinking of the Graph of a Function

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  1. Vertical Stretching or Shrinking of the Graph of a Function • Suppose that a > 0. If a point (x, y) lies on the graph of y = (x), then the point (x, ay) lies on the graph of y = a(x). • If a > 1, then the graph of y = a(x) is a vertical stretching of the graph of y = (x). • If 0 < a <1, then the graph of y = a(x) is a vertical shrinking of the graph of • y = (x)

  2. Horizontal Stretching or Shrinking of the Graph of a Function • Suppose a > 0. If a point (x, y) lies on the graph of y = (x), then the point (, y) lies on the graph of y = (ax). • If 0 < a < 1, then the graph of y = (ax) is horizontal stretching of the graph of y = (x). • If a > 1, then the graph of y = (ax) is a horizontal shrinking of the graph of y = (x).

  3. Reflecting Forming a mirror image of a graph across a line is called reflecting the graph across the line.

  4. REFLECTING A GRAPH ACROSS AN AXIS Example 2 Graph the function. a. y 4 3 2 1 –4 –3 –2 x 4 3 2 –2 –3 –4

  5. REFLECTING A GRAPH ACROSS AN AXIS Example 2 Graph the function. 4 b. 3 y –4 –3 –2 1 4 3 2 –2 –3 –4 x

  6. Reflecting Across an Axis The graph of y = –(x) is the same as the graph of y = (x) reflected across the x-axis. (If a point (x, y) lies on the graph of y = (x), then (x, – y) lies on this reflection. The graph of y = (– x) is the same as the graph of y = (x) reflected across the y-axis. (If a point (x, y) lies on the graph of y = (x), then (– x, y) lies on this reflection.)

  7. Symmetry with Respect to An Axis The graph of an equation is symmetric with respect to the y-axis if the replacement of x with –x results in an equivalent equation. The graph of an equation is symmetric with respect to the x-axis if the replacement of y with –y results in an equivalent equation.

  8. Symmetry with Respect to the Origin The graph of an equation is symmetric with respect to the origin if the replacement of both x with –x and y with –y results in an equivalent equation.

  9. Important Concepts • A graph is symmetric with respect to both x- and y-axes is automatically symmetric with respect to the origin. • A graph symmetric with respect to the origin need not be symmetric with respect to either axis. • Of the three types of symmetry  with respect to the x-axis, the y-axis, and the origin  a graph possessing any two must also exhibit the third type.

  10. y y y x x x 0 0 0

  11. Even and Odd Functions A function  is called an even function if (–x) = (x) for all x in the domain of . (Its graph is symmetric with respect to the y-axis.) A function  is called an odd function is (–x) = –(x) for all x in the domain of . (Its graph is symmetric with respect to the origin.)

  12. DETERMINING WHETHER FUNCTIONS ARE EVEN, ODD, OR NEITHER Example 5 Decide whether each function defined is even, odd, or neither. a. Solution Replacing x in (x) = 8x4 – 3x2with–x gives: Since (–x) = (x) for each x in the domain of the function,  is even.

  13. DETERMINING WHETHER FUNCTIONS ARE EVEN, ODD, OR NEITHER Example 5 Decide whether each function defined is even, odd, or neither. b. Solution The function  is odd because (–x) = –(x).

  14. DETERMINING WHETHER FUNCTIONS ARE EVEN, ODD, OR NEITHER Example 5 Decide whether each function defined is even, odd, or neither. c. Solution Replace x with–x Since (–x) ≠ (x) and (–x) ≠ –(x),  is neither even nor odd.

  15. Vertical Translations

  16. Horizontal Translations

  17. Horizontal Translations If a function gis defined by g(x)= (x–c), where c is a real number, then for every point (x, y) on the graph of , there will be a corresponding point (x + c) on the graph of g. The graph of gwill be the same as the graph of , but translated c units to the right if c is positive or c units to the left if c is negative. The graph is called a horizontal translation of the graph of .

  18. CautionBe careful when translating graphs horizontally. To determine the direction and magnitude of horizontal translations, find the value that would cause the expression in parentheses to equal 0. For example, the graph of y = (x – 5)2 would be translated 5 units to the right of y = x2, because x = + 5 would cause x – 5 to equal 0. On the other hand, the graph of y = (x + 5)2 would be translated 5 units to the left of y = x2, because x = – 5 would cause x + 5 to equal 0.

  19. Summary of Graphing Techniques • In the descriptions that follow, assume that a > 0, h > 0, and k > 0. In comparison with the graph of y = (x): • The graph of y = (x) + kis translated k units up. • The graph of y = (x) – k is translated k units down. • The graph of y = (x + h) is translated h units to the left. • The graph of y = (x– h) is translated h units to the right. • The graph of y = a(x) is a vertical stretching of the graph of y = (x) if a > 1. It is a vertical shrinking if 0 < a < 1. • The graph of y = a(x) is a horizontal stretching of the graph of y = (x) if 0 < a < 1. It is a horizontal shrinking if a > 1. • The graph of y = – (x) is reflected across the x-axis. • The graph of y = (– x) is reflected across the y-axis.

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