# 13.2 Solving Quadratic Equations by Graphing CORD Math Mrs. Spitz Spring 2007.

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13.2 Solving Quadratic Equations by Graphing CORD Math Mrs. Spitz Spring 2007

Objectives Identify standard form coefficients in a standard formula Determine how a parabola opens Find the coordinates of the vertex Sketch a graph of a function.

Assignment 9.3 Worksheet A and B

Identify the values of a, b, and c in the functions. Standard form of a quadratic function: ax 2 + bx + c a, b and c represent coeeficients in the function. a  0

Ex. 1: Identify the values of a, b, and c in the functions. y = -x 2 + 4x – 8 a = -1 b = 4 c = -8

Tell whether the graph opens up or down. Write the equation of the axis of symmetry. If a is positive, the parabola opens up. If a is negative, the parabola opens down.

Ex. 2: Tell whether the graph opens up or down and state the equation of the axis of symmetry. The parabola opens up because a is positive 7.

Find the coordinates of the vertex. In order to find the coordinates of the vertex, you must find the axis of symmetry, then plug in the value you find for x and determine the value for y.

Ex. 3 Find the coordinates of the vertex. Find the value for x using the formula for axis of symmetry.

Ex. 3 Find the coordinates of the vertex. Then substitute the value for x and solve for y. The vertex for this equation is at (1, 19).

Ex. 4: Find the coordinates of the vertex. Make a table of values using 2 x-values to the left and right of the vertex.

xy -37 -2 3 0 1

Ex. 4: Find the coordinates of the vertex. Make a table of values using 2 x-values to the left and right of the vertex. xy -37 -24 3 0 1

Ex. 4: Find the coordinates of the vertex. Make a table of values using 2 x-values to the left and right of the vertex. xy -37 -24 3 04 1

Ex. 4: Find the coordinates of the vertex. Make a table of values using 2 x-values to the left and right of the vertex. xy -37 -24 3 04 17 Next step is to graph the points.

xy -37 -24 3 04 17 vertex