McGraw Hill Glencoe Algebra 1, 2012
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McGraw Hill Glencoe Algebra 1, 2012 View details
6. Graphing Inequalities in Two Variables
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Exercise 8 Page 320

To graph the inequality, you have to draw the boundary line, then decide which side of the boundary line to shade.

Solution: x ≤ - 13/2
Graph:

Practice makes perfect

We want to graph the inequality in order to solve it. It will involve two main steps.

  1. Drawing the boundary line.
  2. Shading half of the plane to show the solution set.

Let's do these two things one at a time.

Boundary Line

To graph the inequality, we have to draw the boundary line. The equation of a boundary line is written by replacing the inequality symbol with an equals sign. Inequality & Boundary Line -3x-2 ≥ 11 & -3x-2 = 11 Before we graph the boundary line, let's first simplify it's equation by isolating the variable on one side.
-3x-2=11
-3x=13
x=13/-3
x=-13/3
Notice that the equation for this boundary line only has one variable. This equation is telling us that each and every point that lies on the line will have an x-coordinate equal to - 133. This gives us a vertical line. Also, the inequality is not strict, so the points on the boundary line are included in the solution set. We show this by drawing a solid line.

Shading the Plane

To decide which side of the boundary line to shade, we will substitute a test point that is not on the boundary line into the given inequality. If the substitution creates a true statement, we shade the region that includes the test point. Otherwise, we shade the opposite region. Let's use (0,0) as our test point.
-3x-2≥ 11
-3( 0)-2? ≥ 11
0-2? ≥ 11
-2 ≱ 11
Since the substitution of the test point did not create a true statement, we will shade the region that does not contain the point.

The x-intercept of the graph is at - 133. Additionally, we shaded the half-plane to the left of our boundary line. Therefore, every possible (x,y) coordinate pair with an x-value that is less than or equal to - 133 lies within the solution set. Let's write our answer as an inequality. x ≤ -13/3