Unformatted text preview: Lesson 26
Quadratic Function:
 a function is quadratic if it is in any of the following forms:
o ()
, where
(
)
o ()
, where
(
)(
), where
o ()
 the degree of a quadratic function is _______
 the graph of a quadratic function a parabola
Vertex of a parabola:
 the turning point, the point where the graph of a quadratic function
changes from increasing to decreasing, or vice versa
 the coordinate of the vertex is either the maximum or minimum
function value
 the coordinate of the vertex is the input where the maximum or
minimum function value occurs
The graph of a quadratic function is a parabola that opens up or down
(why can’t it open to the left or right?).
If the leading coefficient
, the parabola opens up; if the leading
coefficient
, the parabola opens down (why can’t the leading
coefficient
?).
The graph of a quadratic function will always be symmetric about a
vertical line called the line of symmetry. Standard Equation of a Parabola with Vertical Axis:
(
)
)
 the vertex is (
 when
, the parabola opens _______
 when
, the parabola opens _______
 symmetric about the line
, where is the coordinate of the
vertex
A quadratic function in polynomial form ( )
converted to the standard equation of a parabola
completing the square. ( )
⁄ ( ( ( ( ⁄
) ) ( ( ( ( )) )) ) ( ) ( ) can be
)
by This is the standard equation of a parabola with a vertical axis; the vertex
is ( ) or ( ( )). Theorem for Locating the Vertex of a Parabola:
 the vertex of a parabola
has an coordinate
 the vertex is ( ( )) The vertex of a quadratic function can be found by writing the standard
(
)
). The
equation of a parabola,
, and identifying (
vertex can also be found by using the previous theorem, ( ( )). It can also be found by finding the average of the intercepts, then
finding the function value of the coordinate.
Example 1: An object is projected vertically upward from the top of a
building with an initial velocity of 96 ft/sec. Its distance ( ) in feet above
the ground after seconds is given by the equation
() a. Find its maximum distance above the ground. b. Find the height of the building. Example 2: You have 1000 feet of fencing to construct six animal pens.
Each pen is in the shape of rectangle, with the six pens together forming a
large rectangle feet wide by feet long. a. Express the length in terms of the width b. Express the total enclosed area in terms of c. Find the dimensions that maximize the enclosed area. Example 3: A doorway has the shape of a parabolic arch and is 16 feet
high at the center and 8 feet wide at the base. If a rectangular box 7 feet
high must fit through the doorway, what is the maximum width the box
can have? ...
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 Spring '08
 Algebra, Trigonometry, Quadratic equation

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