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 44 Page 321

Practice makes perfect
Let x represent the amount of plastic bottles and y represent the amount of paper products Mr. Jones wants to be removed. The recycling service will not remove more than 50 pounds of waste per week. This constraint can be expressed as an inequality.

x+y ≤ 50

Mr. Jones can spend at most $37.50 per week on recycling. We can write an expression for the weekly total cost of recycling.

0.25 * x+ 0.75 * y This amount should not be more than $37.50, and this constraint can also be expressed as an inequality. 0.25x+ 0.75y ≤ 37.50

We will proceed in steps to graph the inequalities.

First Inequality

Step 1

First we will graph the boundary, which is the related equation. Replace the inequality sign with an equals sign, and solve for y in terms of x.
0.25x+ 0.75y ≤ 37.50
0.75y ≤ - 0.25x + 37.50
y≤ -x/0.75+37.50/0.75
y≤ - 4/3x+50
We will graph the boundary line first. y=- 4/3x+50 Since the number of items cannot be a negative number, the domain and range must contain non-negative numbers. Since the inequality is not strict, we will draw a bold boundary line.

Step 2

Let's choose (0,0) as the test point, as it is the most convenient one for the substitution.
y ≤ - 4/3x+50
0 ≤ -4/3 * 0 + 50
0 ≤ 50

Step 3

Since this result is true, we will shade the region that contains the point (0,0).

Second Inequality

Now let's graph the second inequality.

Step 1

First we will graph the boundary, which is the related equation. Replace the inequality sign with an equals sign, and solve for y in terms of x.
x+y ≤ 50
y ≤ - x + 50
We will graph the boundary line first. y = - x + 50 Since the number of items cannot be a negative number, the domain and range must contain non-negative numbers. Since the inequality is not strict, we will draw a bold boundary line.

Step 2

Let's choose (0,0) as the test point, as it is the most convenient one for the substitution.
y ≤- x + 50
0 ≤ - 0 + 50
0 ≤ 50

Step 3

Since this result is true, we will shade the region that contains the point (0,0).

Now let's draw these two inequalities in the same coordinate system.

The solution set, which is the recycling cost not exceeding Mr.Jones' budget and not exceeding 50 pounds of waste, is the region between the x-axis, the y-axis, and the boundary line y=- 43x+50, since it is shaded twice.