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<b>let </b><font color="Maroon">G</font> be   <a href="graph_1.html#NM1">Graph</a>;<br/><b>let </b><font color="Maroon">x</font> be    <a href="subset_1.html#M1">Element</a> of the <a href="graph_1.html#U1" target="_self">Vertices</a> of <font color="Maroon">G</font>;<br/>



<a NAME="E1:6"/>
the <a href="graph_1.html#U1" target="_self">Vertices</a> of <font color="Maroon">G</font> is  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> 
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E2:6"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U1" target="_self">Vertices</a> of <font color="Maroon">G</font>
 ;<br/>


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