Course: Algebra I / Elementary Algebra
Topic: Linear Equations and Inequalities
Subtopic: Solving Compound Inequalities
Overview
Compound inequalities means to combine two or more inequalities together. There are three ways to do this. Two inequalities can be connected by an "and" (intersection ) which means that the final answer will be those numbers that are in both sets (the overlapping region). Two inequalities can be connected by an "or" (union ) which means that the final answer will be those numbers that are in one set or the other or both -- basically the answer will be both sets all lumped together. The third way to compound inequalities is the "double" kind which means that there are multiple inequalities in one statement like 4<2x-1<10. The key to solving double inequalities is simply to get x isolated in the middle. The final answers to all of these compound inequalities will usually be written in interval notation. Treat this section as an introduction to compound inequalities. This topic will be covered more thoroughly in a College Algebra class.
Objectives
By the end of this topic you should know and be prepared to be tested on:
- 2.5 1 Combine solutions sets connected by "and", "or"
- 2.5.2 Recognize no solution and all solution cases from an "and" or "or" compound inequality
- 2.5.3 Solve all three types of compound linear inequalities: "and", "or", double
Terminology
Define: compound linear inequality, intersection ∩, union ∪
Text Notes
Text:
Intro & Inter Algebra for CS 3ed by Blitzer, sect. 9.1-9.4
- Note that we jumped to chapter 9! It seems logical to do section 9.2 now while we are studying inequalities.
- ch 9.1 is somewhat optional. It basically reviews solving linear inequalities covered in 2.7. It you do choose to study 9.1 SKIP the business applications, revenue function, cost function, profit function, and all the graphing stuff! The only problems from 9.1 that might be included on a quiz are those that are just like those in 2.7.
- ch 9.2 is important. It covers intersections and unions. It focuses on solving compound inequalities including those connected by and, by or, and double inequalities.
- ch 9.2 pg 621 skip the "using technology" box and any exercises involving graphs.
- ch 9.3-9.4 SKIP