222 Chapter 3 Linear Equations in Two Variables GRAPHING CALCULATOR SKILLS Graphing Window—The graphing window on the calculator comes with a standard setting, as shown. The x- and y-values range between -10 and 10, with each tick mark representing 1 unit. 10 –10 10 –10 Equation Editor—The equation editor is what we use to enter equations into the calculator. This is accessed by pressing . Example: Graph x - 2y = 4 on the calculator. We must first solve the equation for y, because this is the only way equations can be entered into the calculator. x - 2y = 4 x - 2y - x = 4 - x -2y=-x + 4 -2y -2 = -x + 4 -2 y = 1 2 x - 2 We can now graph the equation using a graphing calculator. 1 4 2 T u n 2 2 RA H The Table Feature enables us to view ordered pairs that satisfy the equation and are, therefore, points on the graph. 2nd RA H With some equations, we may have to adjust the viewing window to see the graph on the graphing calculator as this next example illustrates. Example: Graph y = -4000x + 32,000. We enter it into the equation editor. When graphed in the standard window, the graph almost looks like a vertical line (which is not the case). We must change the view of the window on the calculator to see the correct graph. To change the view on the calculator, we should find the intercepts by hand to know how to change the window. From example 5b, we know the x-intercept is (8, 0) and the y-intercept is (0, 32,000). We also know that negative x- and y-values do not make sense in this problem. To view a complete graph, we must set the window to see the intercepts. Since the graph crosses the x-axis at (0, 8), we need the maximum x-value to be larger than 8. Let’s use 10. Since the graph crosses the y-axis at (0, 32,000), we need the maximum y-value to be larger than 32,000. Let’s use 35,000. The value for Yscl represents how many units each tick mark on the y-axis represents. If we were drawing this by hand, we might let each tick mark be 5000 units. This is the graph of the equation in the new window. Subtract x from both sides. Simplify. Divide both sides by -2. Simplify.
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