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<b>take </b>
1
;<br/>

<b>let </b><font color="Maroon" title="c1">k</font> be    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="abian.html#D2" target="_self" title="ABIAN:def.2">ABIAN:def 2</a><br/>

<b>assume </b><a NAME="E1:4_2_1"/>
1 <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> 2 <a href="nat_1.html#K4" title="NAT_1:func.4">*</a> <font color="Maroon" title="c1">k</font>
 ;<br/>

<b>hence </b><a NAME="E2:4_2_1"/>
contradiction
 <b>by </b><i><a class="ref" href="nat_1.html#T15" title="NAT_1:th.15">NAT_1:15</a></i>;<br/>


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