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<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="subset_1.html#M1">Element</a> of  <a href="arytm_2.html#K2">REAL+</a> ;<br/>





<b>assume </b><b>that </b><br/><a NAME="E1:27"/><i><font color="Green">E25</font></i>: 
<font color="Maroon">c<sub>2</sub></font> <a href="arytm_2.html#R1">&lt;='</a> <font color="Maroon">c<sub>3</sub></font>
 <b>and </b><br/><a NAME="E2:27"/><i><font color="Green">E26</font></i>: 
<font color="Maroon">c<sub>4</sub></font> <a href="arytm_2.html#R1">&lt;='</a> <font color="Maroon">c<sub>3</sub></font>
 ;<br/>

<b>thus </b><font color="Maroon">c<sub>2</sub></font> <a href="arytm_1.html#K1" target="_self">-'</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="arytm_1.html#K1" target="_self">-'</a> <font color="Maroon">c<sub>4</sub></font></span>)</span> = 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="arytm_2.html#K7">+</a> <font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="arytm_1.html#K1" target="_self">-'</a> <font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="txt" href="arytm_1.html#E2:27"><i><font color="Green">E26</font></i></a>, <a class="txt" href="arytm_1.html#E26"><i><font color="Green">Lemma22</font></i></a></i>
<br/>.= 
<font color="Maroon">c<sub>4</sub></font> <a href="arytm_1.html#K1" target="_self">-'</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="arytm_1.html#K1" target="_self">-'</a> <font color="Maroon">c<sub>2</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="arytm_1.html#E1:27"><i><font color="Green">E25</font></i></a>, <a class="txt" href="arytm_1.html#E26"><i><font color="Green">Lemma22</font></i></a></i>
;<br/>


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