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<b>consider </b><font color="Maroon">S1</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a> , <font color="Maroon">S2</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a> <b> such that </b><br/><a NAME="E2:55_1_1"/><i><font color="Green">E43</font></i>: 
( <font color="Maroon">S</font> <a href="hidden.html#R1">=</a>  <a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font> &amp; <font color="Maroon">S1</font> <a href="substut1.html#K19" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">S2</font> <a href="substut1.html#K19" target="_self">`2</a>  )
 <b>by </b><i>, </i>;<br/>
<b>take </b>
<font color="Maroon">S2</font>
;<br/>

<b>thus </b><a NAME="E3:55_1_1"/>
 ex <font color="Olive">S'</font> being   <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a>  st <br/>( <font color="Maroon">S</font> <a href="hidden.html#R1">=</a>  <a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Olive">S'</font>,<font color="Maroon">S2</font> &amp; <font color="Olive">S'</font> <a href="substut1.html#K19" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">S2</font> <a href="substut1.html#K19" target="_self">`2</a>  )
 <b>by </b><i/>;<br/>


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