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<b>let </b><font color="Maroon" title="c1">x</font>, <font color="Maroon" title="c2">y</font> be   <a href="qc_lang1.html#NM3" title="QC_LANG1:NM.3">bound_QC-variable</a>;<br/>



<b>set </b><font color="Maroon" title="c3">S</font> = <span class="p1"><a href="substut2.html#K2" title="SUBSTUT2:func.2">[</a><span class="default"><a href="cqc_lang.html#K6" title="CQC_LANG:func.6">VERUM</a> ,<span class="p2">(<span class="default"><a href="substut2.html#K3" title="SUBSTUT2:func.3">Sbst</a> <font color="Maroon" title="c1">x</font>,<font color="Maroon" title="c2">y</font></span>)</span></span><a href="substut2.html#K2" title="SUBSTUT2:func.2">]</a></span>;<br/>
<a NAME="E1:19"/>
<span class="p1"><a href="substut2.html#K2" title="SUBSTUT2:func.2">[</a><span class="default"><a href="cqc_lang.html#K6" title="CQC_LANG:func.6">VERUM</a> ,<span class="p2">(<span class="default"><a href="substut2.html#K3" title="SUBSTUT2:func.3">Sbst</a> <font color="Maroon" title="c1">x</font>,<font color="Maroon" title="c2">y</font></span>)</span></span><a href="substut2.html#K2" title="SUBSTUT2:func.2">]</a></span> is <a href="substut1.html#V2" title="SUBSTUT1:attr.2">Sub_VERUM</a>
 
<b>by </b><i><a class="ref" href="substut1.html#D19" title="SUBSTUT1:def.19">SUBSTUT1:def 19</a></i>;<br/>
<b>hence </b><a NAME="E2:19"/>
<a href="cqc_lang.html#K6" title="CQC_LANG:func.6">VERUM</a>  <a href="substut2.html#K4" title="SUBSTUT2:func.4">.</a> <font color="Maroon" title="c1">x</font>,<font color="Maroon" title="c2">y</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="cqc_lang.html#K6" title="CQC_LANG:func.6">VERUM</a> 
 <b>by </b><i><a class="ref" href="sublemma.html#T3" title="SUBLEMMA:th.3">SUBLEMMA:3</a></i>;<br/>


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