FURTHER GRAPHING OF QUADRATIC FUNCTIONS Section 11.6
Further Graphing of Quadratic Functions
Section 11.6
Graph a quadratic equation by plotting points.
Identify the vertex of a parabola.
Quadratic Functions and Their Graphs
Graph by plotting points.
X Y
-2
-1
0
1
2
Section 11.6
2 2 3y x x
22 2 2 3y
21 2 1 3y
20 2 0 3y
21 2 1 3y
22 2 2 3y
X Y
-2 -3
-1 -4
0 -3
1 0
2 7
Quadratic Functions and Their Graphs
Graph by plotting points.
Quadratic Function A function that can be
written in the form y = ax2 + bx + c, where a, b, and c are real numbers and a ≠ 0. The shape of the graph of
a quadratic function is called a parabola.
The maximum or minimum value is called the vertex and has ordered pair (h, k).
All parabolas have an axis of symmetry, which is a vertical line running through the vertex, equation x = h.
Section 11.6
2 2 3y x x
Vertex(-1, -4)
Axis of symmetryx = -1
Quadratic Functions and Their Graphs
Solve . Quadratic Function A function that can be
written in the form y = ax2 + bx + c, where a, b, and c are real numbers and a ≠ 0. Solving the equation
equal to zero is the same as saying y=0, or finding the x-intercepts.
Because of symmetry, the x-intercepts will be equidistant from the vertex.
Section 11.6
2 2 3 0x x
Vertex(-1, -4)
Axis of symmetryx = -1
Quadratic Functions and Their Graphs
Section 11.6
Given an equation of the form y = ax2 + bx + c, the equation of the axis of symmetry can be found using the formula:
Since the axis of symmetry runs through the vertex, this formula also finds the x-coordinate of the vertex. To get the y-coordinate, substitute the found x-coordinate
back into the quadratic equation.
2
bx
a
Deriving a Formula for Finding the Vertex
Section 11.6
To find the vertex of a parabola in standard form: Calculate the x-
coordinate using the formula
Substitute this value into the original function to calculate the y-coordinate
Determine the value of the vertex and graph using the calculator.1.
2.
2
b
a
2 6 8y x x
23 2y x x
3, 1
2316 12,
Quadratic Functions and Their Graphs
An object is thrown upward from the top of a 100-foot cliff. Its height in feet above ground after t seconds is given by the function f(t) = -16t2 +10t +100. Find the maximum height of the object and the number of seconds it took for the object to reach its maximum height. Minimum/Maximum is the VERTEX
After 5/16ths of a second, the object reaches its maximum height of 101 and 9/16 feet.
Section 11.6