FLORIDA Pre-Algebra Teacher’s Guide Vol. A

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Use this guide to accompany Lesson 5.06, Semester A. Substitution and Elimination Methods LESSON GOALS • Solve systems of linear equations using the substitution method. • Solve systems of linear equations using the elimination method. • Identify inconsistent and consistent dependent systems algebraically. FLORIDA STANDARDS • MAFS.8.EE.3.8b. Solve systems of two linear equations in two variables algebraically, and estimate solutions by graphing the equations. Solve simple cases by inspection. PACING One class period, approximately 60 minutes CONTENT BACKGROUND Lessons 5.06, 5.07, and 5.08 work together to introduce students to systems of linear equations. Lesson 5.06 introduces two methods for solving systems that build on students' understanding of systems of equations. The first method, substitution, is the best solution method, when at least one of the equations is solved for a variable. Because the equation will be of the form "y =" or "x =", the value it equals can be substituted into the other equation, creating an equation in one variable. The equation can then be solved. That solution can then be substituted into the other equation to find the value of the other variable. Because errors can be common, students should be encouraged to check their answer by substituting their solution into both equations. The second method is elimination. In this method, students eliminate a variable by adding or subtracting one equation from the other. If necessary, they can multiply one or both equations by a constant in order to assure the elimination of a variable when the equations are added or subtracted. MATERIALS • Reference Guide pages 186–189 • Practice Activity book pages 160–163 • overview and Toolkit presentations KEYWORDS Students can preview definitions of keywords hyperlinked throughout the lesson. • consistent dependent system • contradiction • elimination method • identity • inconsistent system of equations • substitution method SubSTITuTIoN AND ELIMINATIoN METhoDS 257

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