# Calculator Notes for the Texas Instruments TI-83 and TI

DA2CN_773_05.qxd 10/19/05 9:58 Page 38 CHAPTER 5 Calculator Notes for the TI-83 and TI-83/84 Plus Note 5A • Using Matrices to Solve Systems This calculator has a built-in routine to convert a matrix into its equivalent solution form. Enter as MATRIX [A] the matrix that represents the system of equations you wish to solve. Note that this matrix must have one more column than its number of rows; for example, its dimensions might be 2 3, 3 4, or 7 8. In the Home screen, press 2nd [MATRIX], select [MATH], and select B:rref(. Then press 2nd [MATRIX] 1 ([A]) ) ENTER . (On the TI-83, press MATRX for the matrix menu.) 2x y 1 As an example consider the system 3x 2y 19 The solution to the system is x 3 and y 5. Note 5B • Inequality Symbols This calculator can test or evaluate an expression to determine whether it is true or false. This is called a Boolean test, after the mathematician Charles Boole. To find the equality and inequality symbols, press 2nd [TEST]. An expression is evaluated as 0 if it is false and as 1 if it is true. Note 5C • Graphing Inequalities in Two Variables This calculator can graph an inequality in two variables by shading the screen above or below the graph of an equation. Enter an equation into the Y screen. Then, in that same line, move the cursor as far left as it will go and press ENTER . Each time you press ENTER , the graph style changes and is indicated by the flashing cursor. To see the graph, press GRAPH . To graph the inequality y 2 x, enter the equation for the line Y1 2 x into the Y screen. Then, move the cursor to the left of Y1 and press ENTER ENTER to set the graph style to shade the portion of the screen above the line. Finally, press GRAPH . [10, 10, 1, 10, 10, 1] You can graph a system of inequalities by graphing two (or more) inequalities on the same screen. y 2 x To graph the system of inequalities y 1 x graph the first inequality as previously shown. Then, enter the equation for the line Y2 1 x into the Y screen. Move the cursor all the way to the left and press ENTER ENTER ENTER to set the graph style to shade the portion of the screen below the line. Finally, press GRAPH . 38 Discovering Algebra Calculator Notes for the Texas Instruments TI-83 and TI-83/84 Plus [10, 10, 1, 10, 10, 1] ©2007 Key Curriculum Press DA2CN_773_05.qxd 10/19/05 14:37 Page 39 TI-83 and TI-83/84 Plus Note 5C/App • Graphing Inequalities Using the Inequalz App An inequality graphing application is available for the TI-83 Plus and TI-84 Plus. It comes preloaded on the TI-84 Plus, and can be downloaded for the TI-83 Plus. Once you have the application on your calculator, follow these steps to use it. Press APPS , scroll down to :Inequalz, and press ENTER . Press any key to continue. Enter an expression and move onto the equals symbol. You’ll see five choices, , , , , and , appear at the bottom of the screen. Press ALPHA then one of the five keys in the top row of your calculator to select the equality or inequality key you want. (For example, press ALPHA [F2] to choose .) Press GRAPH to graph the equation or inequality. The Inequalz App is particularly useful if you want to graph the solution to a system of inequalities. For example, three inequalities are graphed here. It is not easy to identify the solution region. To shade only the solution region, press ALPHA [F1] to select Shades. Select 1:Ineq Intersection. Now only the solution region—the region where all three inequalities intersect—is shown. When finished graphing inequalities, quit the application by pressing scrolling down to :Inequalz, pressing ENTER , and selecting 2:Quit Inequal. ©2007 Key Curriculum Press APPS , Discovering Algebra Calculator Notes for the Texas Instruments TI-83 and TI-83/84 Plus 39

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