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| 8 Theory slides |
| 10 Exercises - Grade E - A |
| Each lesson is meant to take 1-2 classroom sessions |
Here are a few recommended readings before getting started with this lesson.
x | y=∣3x−6∣+3 | y |
---|---|---|
0 | y=∣3(0)−6∣+3 | 9 |
1 | y=∣3(1)−6∣+3 | 6 |
2 | y=∣3(2)−6∣+3 | 3 |
3 | y=∣3(3)−6∣+3 | 6 |
4 | y=∣3(4)−6∣+3 | 9 |
Plot the points and draw the boundary line. Since the given inequality is strict, the boundary line will be dashed.
x=0, y=0
Zero Property of Multiplication
Subtract terms
∣-6∣=6
The test point is not a solution, so the region that does not contain the test point — inside the V-shaped graph — represents the solution set for the inequality. Finally, the appropriate region can be shaded.
Analyze the graph of the given absolute value inequality in two variables to determine the proper inequality symbol.
LHS+4=RHS+4
a=22⋅a
Factor out 25
∣a⋅b∣=∣a∣⋅∣b∣
∣∣∣∣∣25∣∣∣∣∣=25
a=-(-a)
x | -25∣x+2∣+4 | y=-25∣x+2∣+4 |
---|---|---|
-4 | -25∣-4+2∣+4=-1 | -1 |
-3 | -25∣-3+2∣+4=1.5 | 1.5 |
-2 | -25∣-2+2∣+4=4 | 4 |
-1 | -25∣-1+2∣+4=1.5 | 1.5 |
0 | -25∣0+2∣+4=-1 | -1 |
Finally, plot the points and draw the absolute value equation.
As can be seen, the mirror has a V-shape with a vertex of (-2,4) in the coordinate plane.
x | y=0.4∣x−4∣+3 | y |
---|---|---|
0 | y=0.4∣0−4∣+3 | 4.6 |
2 | y=0.4∣2−4∣+3 | 3.8 |
4 | y=0.4∣4−4∣+3 | 3 |
6 | y=0.4∣6−4∣+3 | 3.8 |
8 | y=0.4∣8−4∣+3 | 4.6 |
Plot the points and draw the boundary line. Since the inequality is non-strict, the boundary line will be solid. Note that only positive values of x and y makes sense in the context of the situation.
In the same auction, Emily was also interested in the object that Ignacio bought. Emily knows that Ignacio will sell it sooner or later. The maximum amount of money Emily can allocate to buy Ignacio's object is represented by the following graph.
To write the equation of the boundary line, use the vertex form of an absolute value equation y=a∣x−h∣+k, where (h,k) is the vertex of the absolute value equation.
On the given graph, x represents the years after the auction and y represents the price of the object in thousands of dollars. Since Emily can allocate any amount less than $3800 for the object 4 years after the auction, these values correspond to point (4,3.8), which is the vertex of the boundary line.
x=10, y=5
Subtract term
∣6∣=6
LHS−3.8=RHS−3.8
LHS/6=RHS/6
Rearrange equation
less than,<.
Any point in this region is the solution to both inequalities. In the context of the last two examples, Ignacio and Emily can make a deal as long as the values stay in that region.
Which graph represents the solution set of the absolute value inequality y≥∣3x−12∣?
We will follow three steps to graph the given absolute value inequality.
The boundary line of an inequality can be determined by replacing the inequality symbol with an equal sign. Inequality & Boundary Line y ≥ |3x-12| & y = |3x-12| Notice that the equation of the boundary line is an absolute value equation. Let's rewrite it in vertex form to find its vertex. y = |3x-12| ⇓ y = 3|x- 4|+ 0 Its vertex is ( 4, 0). The graph of the boundary line should be symmetric about the line x=4. To graph the boundary line, we can make a table of values using some x-values greater and less than 4.
x | |3x-12| | y = |3x-12| |
---|---|---|
2 | |3( 2)-12| | 6 |
3 | |3( 3)-12| | 3 |
4 | |3( 4)-12| | 0 |
5 | |3( 5)-12| | 3 |
6 | |3( 6)-12| | 6 |
We now plot the points and draw the boundary line. Since the inequality is non-strict, the boundary line will be solid.
In order to decide which part of the plane to shade, we can test a point which is not on the boundary line. Let's test the point ( 0, 0).
If the point satisfies the inequality, we shade the region that contains the point. Otherwise, we shade the region that does not contain the point. Let's substitute the test point into the given inequality.
Since the point does not satisfy the inequality, it is not a solution to the inequality.
We will shade the region that does not contain the point because the test point is not a solution.
We can see that Graph A is the same as the graph we drew.
Which graph represents the solution set of the absolute value inequality y<∣0.75x∣+2?
We will follow three steps to graph the given absolute value inequality.
The boundary line of an inequality can be determined by replacing the inequality symbol with an equal sign. Inequality & Boundary Line y < |0.75x|+2 & y = |0.75x|+2 Notice that the equation of the boundary line is an absolute value equation. Let's rewrite it in vertex form to find its vertex. y = |0.75x|+2 ⇓ y = 0.75|x- 0|+ 2 Its vertex is ( 0, 2). The graph of the boundary line should be symmetric about the y-axis. To graph the boundary line, we can make a table of values using some x-values below and above 0.
x | |0.75x|+2 | y = |0.75x|+2 |
---|---|---|
- 4 | |0.75( - 4)|+2 | 5 |
0 | |0.75( 0)|+2 | 2 |
4 | |0.75( 4)|+2 | 5 |
We now plot the points and draw the boundary line. Since the inequality is strict, the boundary line will be dashed.
In order to decide which part of the plane to shade, we can test a point which is not on the boundary line. Let's test the point ( 0, 0).
If the point satisfies the inequality, we shade the region that contains the point. Otherwise, we shade the region that does not contain the point. Let's substitute the test point into the given inequality.
Since the point satisfies the inequality, it is a solution to the inequality.
We will shade the region that contains the point because the test point is a solution.
This graph matches with the graph in C.
Which graph represents the solution set of the absolute value inequality y+10>5∣∣∣41x+2∣∣∣?
We will follow three steps to graph the given absolute value inequality.
In this case, we will first isolate the y-variable.
The boundary line of an inequality can be determined by replacing the inequality symbol with an equal sign. Inequality & Boundary Line y > 5 |1/4x+2|-10 & y = 5 |1/4x+2|-10 Notice that the equation of the boundary line is an absolute value equation. Let's rewrite it in vertex form to find its vertex.
We can now identify the vertex. y = 5/4|x+8|-10 ⇓ y = 5/4|x-( - 8)|+ ( - 10) Its vertex is ( - 8, - 10). Therefore, the graph of the boundary line should be symmetric about the line x=- 8. To graph the boundary line, we can make a table of values using some x-values below and above - 8.
x | 5/4|x+8|-10 | y=5/4|x+8|-10 |
---|---|---|
- 16 | 5/4| - 16+8|-10 | 0 |
- 8 | 5/4| - 8+8|-10 | - 10 |
0 | 5/4| 0+8|-10 | 0 |
We now plot the points and draw the boundary line. Since the inequality is strict, the boundary line will be dashed.
In order to decide which part of the plane to shade, we can test a point which is not on the boundary line. Let's test the point ( - 8, 0).
If the point satisfies the inequality, we shade the region that contains the point. Otherwise, we shade the region that does not contain the point. Let's substitute the test point into the given inequality.
Since the point satisfies the inequality, it is a solution to the inequality.
We will shade the region that contains the point because the test point is a solution.
This graph matches with the graph in option B.
Write an inequality for the given graph.
To write an inequality for the graph, we will follow two steps.
Let's get started by focusing on the boundary line.
We see that the vertex of the boundary line is (- 4,0). Recall the vertex form of an absolute value equation whose vertex is at (h,k). y = a|x-h|+k Since the vertex of the boundary line is ( - 4, 0), the corresponding values can be substituted and the expression simplified.
We can substitute a point on the boundary line, different than the vertex, to find the value of a. We know that (- 6,2) lies on the boundary line. Let's substitute these values into our equation and solve for a!
We can now write the equation of the boundary line. y = 1|x+4| ⇔ y = |x+4|
Now that we have the equation of the boundary line, we will determine the inequality symbol.
Since the boundary line is dashed, the inequality will be strict, meaning that it is either < or >. The shaded region is below the boundary line. That is, the y-values are less than |x+4|. Therefore, the inequality symbol should be <. Boundary Line: & y = |x+4| Inequality:& y < |x+4|
We can check our answer by substituting a point in the shaded region into our function and simplifying. If the solution is true, we know our answer is correct. Let's try (- 3,- 2).
We can conclude that the solution set of the inequality is the given graph.
Write an inequality for the given graph.
To write an inequality for the graph, we will follow two steps.
Let's get started by focusing on the boundary line.
We see that the vertex of the boundary line is (5,- 1). Recall the vertex form of an absolute value equation whose vertex is at (h,k). y = a|x-h|+k Since the vertex of the boundary line is ( 5, - 1), the corresponding values can be substituted.
We can substitute a point on the boundary line to find the value of a. Let's use (0,- 5).
We can now write the equation of the boundary line. y = - 0.8|x-5|-1
Now that we have the equation of the boundary line, we will determine the inequality symbol.
Since the boundary line is solid, the inequality will be non-strict, meaning that it is either ≤ or ≥. The shaded region is above the boundary line. That is, the y-values are greater than or equal to |x+4|. Therefore, the inequality symbol should be ≥. Boundary Line: & y = - 0.8|x-5|-1 Inequality:& y ≥ - 0.8|x-5|-1
We can check our answer by substituting a point in the shaded region. If the inequality is correct, then it will produce a true statement. Let's try (0,0).
We can conclude that the solution set of the inequality is the given graph.