Reflection: Developing a Conceptual Understanding Solve Inequalities Using Multiplication and Division - Section 1: Introduction

 

When writing this lesson I had to decide whether or not to present flipping the comparison symbol as a procedure that you just do whenever dividing or multiplying both sides by a negative value.  I felt it would be better to let them "discover" it instead.  My hope is that this will encourage a couple of habits in my students.  

One habit comes from mathematical practice 6 - attend to precision.  The standard says students are able to "state the meaning of the symbols they choose, including using the equal sign".  I imagine this can extend to the use of the inequality symbols as well.  The fact that -2x < 8  has the solution x > -4 requires students are very mindful of how they are using the symbols.  

Another habit comes from mathematical practice 3 - construct viable arguments and critique the reasoning of others.  A solution to an inequality is a simple case to exercise this habit.  Wehn solving an inequality like -2x < 8 we can build a case for seeing why the solution is NOT x < -4.  Students can explain by their thinking by trying values and evaluating the validity of the inequality.

 

  Flipping the Inequality
  Developing a Conceptual Understanding: Flipping the Inequality
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Solve Inequalities Using Multiplication and Division

Unit 4: Expressions and Equations
Lesson 13 of 20

Objective: SWBAT solve inequalities using multiplication and division

Big Idea: Inequalities and equations are solved in a similar manner; only the solution is different.

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