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CHAPTER 4 QUADRATIC FUNCTIONS
AND EQUATIONS
4.1 Quadratic Functions and Transformations
DEFINITIONS
   A parabola is the graph of a quadratic function.
       A parabola is a “U” shaped graph

       The parent Quadratic Function is




                                    Vertex at (0, 0)
                                    Axis of Symmetry at x = 0
DEFINITIONS
   The vertex form of a quadratic function makes it
    easy to identify the transformations



 The axis of symmetry is a line that divides the
  parabola into two mirror images (x = h)
 The vertex of the parabola is (h, k) and it
  represents the intersection of the parabola and the
  axis of symmetry.
REFLECTION, STRETCH, AND COMPRESSION
   Working with functions of the form
       The      determines the “width” of the parabola
         If the          the graph is vertically stretched (makes the “U”
          narrow)
         If               the graph is vertically compressed (makes
          the “U” wide)
       If a is negative, the graph is reflected over the              x–
        axis
MINIMUM AND MAXIMUM VALUES
 The minimum value of a function is the least y –
  value of the function; it is the y – coordinate of the
  lowest point on the graph.
 The maximum value of a function is the greatest
  y – value of the function; it is the     y–
  coordinate of the highest point on the graph.

   For quadratic functions the minimum or maximum
    point is always the vertex, thus the minimum or
    maximum value is always the         y – coordinate
    of the vertex
TRANSFORMATIONS – USING VERTEX FORM
  Remember transformations from Chapter 2
  The vertex form makes identifying transformations
   easy

      a gives you information about stretch, compression, and
       reflection over the x – axis
      h gives you information about the horizontal shift
      k gives you information about the vertical shift


      The vertex is at (h, k)
      The axis of symmetry is at x = h
TRANSFORMATIONS – USING VERTEX FORM
 Graphing Quadratic Functions:
 1. Identify and Plot the vertex and axis of symmetry

 2. Set up a Table of Values. Choose x – values to the
    right and left of the vertex and find the
    corresponding y – values
 3. Plot the points and sketch the parabola
EXAMPLE: GRAPH EACH FUNCTION. DESCRIBE
HOW IT WAS TRANSLATED FROM
EXAMPLE: GRAPH EACH FUNCTION. DESCRIBE
HOW IT WAS TRANSLATED FROM
EXAMPLE: GRAPH EACH FUNCTION. DESCRIBE
HOW IT WAS TRANSLATED FROM
EXAMPLE: GRAPH EACH FUNCTION. DESCRIBE
HOW IT WAS TRANSLATED FROM
TRANSFORMATIONS – USING VERTEX FORM
 Writing the equations of Quadratic Functions:
 1. Identify the vertex (h, k)

 2. Choose another point on the graph (x, y)

 3. Plug h, k, x, and y into                        and
    solve for a
 4. Use h, k, and a to write the vertex form of the
    quadratic function
EXAMPLE: WRITE A QUADRATIC FUNCTION TO
MODEL EACH GRAPH
EXAMPLE: WRITE A QUADRATIC FUNCTION TO
MODEL EACH GRAPH