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| Summary |
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- A half-plane in the x-y plane is called a closed half-plane if the points on the line separating the half-planes are also included in the half-plane.
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The graph of a linear inequation involving sign ' ' or ' ' is a closed half-plane. |
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- A half-plane in the x-y plane is called an open half-plane if the points on the line separating the half-planes are not included in the half-plane.
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| The graph of a linear inequation involving sign '<' or '>' is an open half-plane. |
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- Two or more linear inequations are said to constitute a system of linear inequations.
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- The solution set of a system of linear inequations is defined as the intersection of solution sets of linear inequations in the system.
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| General Rules |
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- If a > b, then we have the following rules:
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- a + l > b +
l for any l
 R
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- a - l > b -
l for any l
 R
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- la > lb for any positive real number
l
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- la < lb for any negative real number
l
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