Topic: Functions and Graphs II
Subtopic: Parabolas I - Algebraic Approach
Overview
This topic is really fun and useful! We are going to explore the graphs of quadratic functions. These functions all have the same basic U-shape graph called a parabola. A parabola's equation takes on two forms: the standard form of a parabola y=a(x-h)2+k and the general form of a parabola y=ax2+bx+c. This lesson covers analyzing these equations algebraically and producing the graphs manually.
Objectives
By the end of this topic you should know and be prepared to be tested on:
- 12.1.1 Know the graph of the basic parabola y=x2 including specific points that lie on it
- 12.1.2 Recognize and be able to perform reflections (flips across the x-axis), stretches, vertical shifts (up or down), and horizontal shifts (left or right)
- 12.1.3 Know what values in the parabola's equation controls the above features (shifts, etc.) of the graph
- 12.1.4 Given either form of a parabola, know that the a-value gives you information about which way the parabola opens and how wide/narrow that opening is.
- 12.1.5 Given the standard form of a parabola, be able to identify the a, h, and k-values and know that the k-term is the shift up/down, the h-term is the shift left/right, and the vertex is the point (h,k).
- 12.1.6 Given the general form of a parabola, be able to identify the a, b, and c-values and know the vertex is the point (-b/(2a),f(-b/(2a))).
- 12.1.7 Given either form of a parabola, know how to algebraically find the y-intercept (by letting x=0) and the x-intercepts (by letting y=0 and solving for x using factoring, the root method, CTS, or the quadratic formula as needed)
- 12.1.8 Pull all the known information about a parabola together and manually produce its graph
Terminology
Define: parabola, standard vs. general form of a parabola, vertex, reflection about the x-axis, vertical translation (shift), horizontal shift, general form's vertex formula Vx=-b/(2a) (memorize it!)
Text Notes
Text:
Intro & Inter Algebra for CS 3ed by Blitzer, sect. 11.3
- This text section covers too much material so is split into two lecture notes, the first focusing on the algebraic approach to parabolas and the second focusing on the graphic approach.
- examples 1-2 Given the standard form of the parabola, be sure that you can find the vertex and all intercept points algebraically. You should also be able to verify this information graphically too. Practice both approaches!
- examples 3-4 Given the general form of the parabola be sure that you can find the vertex and all intercept points algebraically. You should also be able to verify this information graphically too. Practice both approaches!