Topic: Lines and their Graphs
Subtopic: Equations of Lines
Overview
The slope-intercept method is the most useful method for graphing a linear function. Be sure to memorize the formula y=mx+b and learn to use it well! Be sure that you are able to graph a line from its equation manually by each of the following methods:
- Plug-n-chug method
- Intercept method
- Slope-intercept method
So far we have primarily been starting with a linear equation and then producing the graph. But you should also be able to work that process backwards, beginning with the graph (or information about the graph) and finding the equation of the line. This will allow us to take real-life data and find a representative linear equation thus opening up even more avenues for solving practical applications.
Objectives
By the end of this topic you should know and be prepared to be tested on:
- 4.3.1 Given the equation of a line, find its slope and y-intercept
- 4.3.2 Given the graph of a line, find its slope, y-intercept, and equation
- 4.3.3 Graph a line by the slope-intercept method
- 4.3.4 Given the slope and a point on the line (either the y-intercept or one that is not the y-intercept), find its equation
- 4.3.5 Given two points on a line, find its slope then equation
- 4.3.6 Given various information about a line (including info about parallel, perpendicular, horizontal, or vertical lines), find its equation
- 4.3.7 Given the graph of a line, find the slope-intercept form of its equation
- 4.3.8 Describe what slope and y-intercept value mean in practical terms
- 4.3.9 Understand applications of the slope-intercept equation of the line
Terminology
Define: slope-intercept formula for the equation of a line y=mx+b (memorize it!), point-slope formula for the equation of a line y-y1=m(x-x1) (memorize it!)
Text Notes
Text:
Intro & Inter Algebra for CS 3ed by Blitzer, sect. 3.4-3.5
These sections are super important filled with formulas, terminology, and processes. Spend significant time learning them well. The next chapter deals with "systems of linear equations" where the graphs will have more than one linear equation and we will be analyzing how they connect including finding intersection points and interpreting this information in terms of fairly advanced applications. I cannot stress enough how important it is to have the processes of "equation -> graph" and "graph -> equation" down well before we start adding the additional lines to form multi-equation multi-variable systems!