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<b>consider </b><font color="Maroon">a</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E2:7_1"/><i><font color="Green">E9</font></i>: 
for <font color="Olive">b</font> being   <a href="hidden.html#M1">set</a>   holds <br/>( <font color="Maroon">P<sub>1</sub></font>[<font color="Maroon">a</font>] or <font color="Maroon">P<sub>2</sub></font>[<font color="Olive">b</font>] )
 <b>by </b><i/>;<br/>
<a NAME="E3:7_1"/>
( not for <font color="Olive">b</font> being   <a href="hidden.html#M1">set</a>  holds  <font color="Maroon">P<sub>2</sub></font>[<font color="Olive">b</font>] implies <font color="Maroon">P<sub>1</sub></font>[<font color="Maroon">a</font>] )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E4:7_1"/>
(  ex <font color="Olive">a</font> being   <a href="hidden.html#M1">set</a>  st <font color="Maroon">P<sub>1</sub></font>[<font color="Olive">a</font>] or for <font color="Olive">b</font> being   <a href="hidden.html#M1">set</a>  holds  <font color="Maroon">P<sub>2</sub></font>[<font color="Olive">b</font>] )
 ;<br/>


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