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<b>let </b><font color="Maroon">H</font> be   <a href="zf_lang.html#NM2">ZF-formula</a>;<br/><b>let </b><font color="Maroon">x</font> be   <a href="zf_lang.html#NM1">Variable</a>;<br/><b>let </b><font color="Maroon">y</font> be   <a href="zf_lang.html#NM1">Variable</a>;<br/>





<b>assume </b><a NAME="E1:171"/>
<font color="Maroon">H</font> is <a href="zf_lang.html#V4">negative</a>
 ;<br/>

<a NAME="E2:171"/><b>then </b>
( <font color="Maroon">H</font> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> is <a href="zf_lang.html#V4">negative</a> &amp; <font color="Maroon">H</font> <a href="hidden.html#R1">=</a>  <a href="zf_lang.html#K6">'not'</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K20">the_argument_of</a> <font color="Maroon">H</font></span>)</span> )
 
<b>by </b><i>, <a class="ref" href="zf_lang.html#D30">ZF_LANG:def 30</a></i>;<br/>
<a NAME="E3:171"/><b>then </b>
( <font color="Maroon">H</font> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="hidden.html#R1">=</a>  <a href="zf_lang.html#K6">'not'</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K20">the_argument_of</a> <span class="p2">(<span class="default"><font color="Maroon">H</font> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font></span>)</span></span>)</span> &amp; <font color="Maroon">H</font> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="hidden.html#R1">=</a>  <a href="zf_lang.html#K6">'not'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="zf_lang.html#K20">the_argument_of</a> <font color="Maroon">H</font></span>)</span> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font></span>)</span> )
 
<b>by </b><i><a class="ref" href="zf_lang1.html#T66" target="_self">Th66</a>, <a class="ref" href="zf_lang.html#D30">ZF_LANG:def 30</a></i>;<br/>
<b>hence </b><a NAME="E4:171"/>
 <a href="zf_lang.html#K20">the_argument_of</a> <span class="p1">(<span class="default"><font color="Maroon">H</font> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K20">the_argument_of</a> <font color="Maroon">H</font></span>)</span> <a href="zf_lang1.html#K6" target="_self">/</a> <font color="Maroon">x</font>,<font color="Maroon">y</font>
 <b>by </b><i><a class="ref" href="finseq_1.html#T46">FINSEQ_1:46</a></i>;<br/>


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