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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font> be   <a href="nat_1.html#NM1">Nat</a>;<br/>



<b>assume </b><a NAME="E1:23"/><i><font color="Green">E14</font></i>: 
<font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font> <a href="int_2.html#R2">are_relative_prime</a> 
 ;<br/>

<b>assume </b><a NAME="E2:23"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="abian.html#V1">even</a>
 ;<br/>

<a NAME="E3:23"/><b>then </b><i><font color="Green">E15</font></i>: 
2 <a href="nat_1.html#R1">divides</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="pepin.html#T22">PEPIN:22</a></i>;<br/>
<b>assume </b><a NAME="E4:23"/>
<font color="Maroon">c<sub>2</sub></font> is <a href="abian.html#V1">even</a>
 ;<br/>

<a NAME="E5:23"/><b>then </b>
2 <a href="nat_1.html#R1">divides</a> <font color="Maroon">c<sub>2</sub></font>
 
<b>by </b><i><a class="ref" href="pepin.html#T22">PEPIN:22</a></i>;<br/>
<b>hence </b><a NAME="E6:23"/>
contradiction
 <b>by </b><i><a class="txt" href="pythtrip.html#E1:23"><i><font color="Green">E14</font></i></a>, <a class="txt" href="pythtrip.html#E3:23"><i><font color="Green">E15</font></i></a>, <a class="ref" href="pythtrip.html#D1" target="_self">Def1</a></i>;<br/>


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