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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font>, <font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</sub></font> be    <a href="pnproc_1.html#M1" target="_self">marking</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>







<b>assume </b><a NAME="E1:45"/>
<font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font> <a href="pnproc_1.html#R2" target="_self">c=</a> <font color="Maroon">c<sub>4</sub></font>
 ;<br/>

<b>then </b><span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>3</sub></font> = 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <span class="p4">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="pnproc_1.html#K4" target="_self">+</a> <span class="p3">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="ref" href="pnproc_1.html#T27" target="_self">Th27</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3">(<span class="default"><span class="p4">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <span class="p5">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="ref" href="pnproc_1.html#T23" target="_self">Th23</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <span class="p3">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="ref" href="pnproc_1.html#T28" target="_self">Th28</a></i>
<br/>.= 
<font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
<b>by </b><i><a class="ref" href="pnproc_1.html#T28" target="_self">Th28</a></i>
;<br/>
<b>hence </b><a NAME="E3:45"/>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="pnproc_1.html#K5" target="_self">-</a> <font color="Maroon">c<sub>3</sub></font> <a href="pnproc_1.html#R1" target="_self">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="pnproc_1.html#K5" target="_self">-</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="pnproc_1.html#K4" target="_self">+</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
 ;<br/>


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