compound
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Compound. Inequalities. You already know inequalities. Often they are used to place limits on variables. That just means x can be any number equal to 9 or less than 9. Sometimes we put more than one limit on the variable:. - PowerPoint PPT PresentationTRANSCRIPT
9x
You already know inequalities.
Often they are used to place limits on variables.
That just means x can be any number equal to 9 or less than
9.
Sometimes we put more than one limit on the variable:
Now x is still less than or equal to 9, but it must also be greater than or
equal to –7.
7 and 9 xx
7 and 9 xx
Let’s look at the graph:
0 5 10 15-20 -15 -10 -5-25 20 25
The upper limit is 9. Because x can be equal to 9, we mark it with a filled-in
circle.
0 5 10 15-20 -15 -10 -5-25 20 25
The lower limit is -7. We also need to mark it with a filled-in
circle.
7 and 9 xx
Where are they found on the graph?
Yes!
It is less than or equal to 9?What about –15?
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There are other numbers that satisfy both conditions.
7 and 9 xx
15
It is also greater than or equal to -7?
What about –15?
0 5 10 15-20 -15 -10 -5-25 20 25
7 and 9 xx
15 No!
Where are they found on the graph?
Because the word and is used, a number on the graph
needs to satisfy both parts of the inequality.
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7 and 9 xx
15
Yes!720
So let’s try 20. Does 20 satisfy both conditions?
0 5 10 15-20 -15 -10 -5-25 20 25
7 and 9 xx
20
?
15
No!920
So let’s try 20. Does 20 satisfy both conditions?
0 5 10 15-20 -15 -10 -5-25 20 25
7 and 9 xx
20
?
15
Since 20 does not satisfy both conditions, it can’t
belong to the solution set.
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7 and 9 xx
2015
We need to choose a number from that region.
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7 and 9 xx
2015
You want to choose 0?Good choice! 0 is usually the easiest number to work
with.0
If one number in a region completely satisfies an
inequality,
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7 and 9 xx
2015 0
you can know that every number in that region
satisfies the inequality.
And
Shade between the two numbers.
Make sure you think if it makes sense because no solutions can
exist.0 5 10 15-20 -15 -10 -5-25 20 25
7 and 9 xx
tells us we want an open circle,The first sign
First we mark the boundary points:
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1or 12 xx
The boundary points divide the line into three regions:
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1or 12 xx
1 2 3
We need to test one point from each region.
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1or 12 xx
10 1210
No!?-110
Yes!?
Notice that the word used is or,
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1or 12 xx
10 1210
No! 1210
Yes!
instead of and.
Or means that a number
0 5 10 15-20 -15 -10 -5-25 20 25
1or 12 xx
10 1210
No! 1210
Yes!
only needs to meet one condition.
Because –10 meets one condition,
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1or 12 xx
1210 1210 Yes!
10
the region to which it belongs . . .. . . belongs to the graph.
Because –1 meets neither condition,
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1or 12 xx
125 15 5
No! No!
the numbers in that regionwill not satisfy the inequality.
Again, 15 meets one condition
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1or 12 xx
1215 115 15
Yes!
so we need to shade that region.
Or shade outside the boundaries
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1or 12 xx
Make sure you think because no solutions do exist
A quick review:
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1. Find and mark the boundary points.2. Test points from each region.3. Shade the regions that satisfy the inequality.or and or
To graph a compound inequality:
Given the graph below, write the inequality.
First, write the boundary points.
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Since x is between the boundary points on the
graph,
15 20
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it will be between the boundary points in the inequality.
xx
20 15 x
Since x is between the boundary points on the
graph,
x0 5 10 15-20 -15 -10 -5-25 20 25
it will be between the boundary points in the inequality.
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Because the x-values are not between the boundary points
on the graph,we won’t write x between the
boundary points in the equation.
x x 5 10
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x xx105x
We will use the word, or, instead:Remember that or means
a number has to satisfy only one of the conditions.
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Is there any one number that belongs to both shaded
sections in the graph?
xx 10or 5
Say NO!NO!
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xx 10or 5
So it would be incorrect to use and. And implies that a
number meets both conditions.
. . . you remember that a compound inequality is just two
inequalities put together.
9325 x
Solving compound inequalities is easy if . . .
932 x325 x 9325 x