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<b>let </b><font color="Maroon" title="c3">SF</font> be   <a href="closure2.html#NM1" title="CLOSURE2:NM.1">SubsetFamily</a> of <font color="Maroon" title="c2">M</font>;<br/>

<b>assume </b><a NAME="E1:48_1_1"/><i><font color="Green" title="E25">A1</font></i>: 
<font color="Maroon" title="c3">SF</font> is <a href="closure2.html#V2" title="CLOSURE2:attr.2">absolutely-additive</a>
 ;<br/>

<b>reconsider </b><font color="Maroon" title="c4">a</font> =  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  as   <a href="closure2.html#NM1" title="CLOSURE2:NM.1">SubsetFamily</a> of <font color="Maroon" title="c2">M</font> <b>by </b><i><a class="ref" href="xboole_1.html#T2" title="XBOOLE_1:th.2">XBOOLE_1:2</a></i>;<br/>
<a NAME="E3:48_1_1"/>
<span class="p1"><a href="closure2.html#K5" title="CLOSURE2:func.5">|:</a><span class="default"><font color="Maroon" title="c4">a</font></span><a href="closure2.html#K5" title="CLOSURE2:func.5">:|</a></span> <a href="pboole.html#R6" title="PBOOLE:pred.6">=</a>  <a href="pboole.html#K1" title="PBOOLE:func.1">[0]</a> <font color="Maroon" title="c1">I</font>
 
<b>by </b><i><a class="ref" href="closure2.html#D4" target="_self" title="CLOSURE2:def.4">Def4</a></i>;<br/>
<a NAME="E4:48_1_1"/><b>then </b><i><font color="Green" title="E26">A2</font></i>: 
 <a href="mboolean.html#K2" title="MBOOLEAN:func.2">union</a> <span class="p1"><a href="closure2.html#K5" title="CLOSURE2:func.5">|:</a><span class="default"><font color="Maroon" title="c4">a</font></span><a href="closure2.html#K5" title="CLOSURE2:func.5">:|</a></span> <a href="pboole.html#R6" title="PBOOLE:pred.6">=</a>  <a href="pboole.html#K1" title="PBOOLE:func.1">[0]</a> <font color="Maroon" title="c1">I</font>
 
<b>by </b><i><a class="ref" href="mboolean.html#T22" title="MBOOLEAN:th.22">MBOOLEAN:22</a></i>;<br/>
<a NAME="E5:48_1_1"/>
<font color="Maroon" title="c4">a</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a> <font color="Maroon" title="c3">SF</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T2" title="XBOOLE_1:th.2">XBOOLE_1:2</a></i>;<br/>
<b>hence </b><a NAME="E6:48_1_1"/>
 <a href="pboole.html#K1" title="PBOOLE:func.1">[0]</a> <font color="Maroon" title="c1">I</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c3">SF</font>
 <b>by </b><i><a class="txt" href="closure2.html#E1:48_1_1"><i><font color="Green" title="E25">A1</font></i></a>, <a class="txt" href="closure2.html#E4:48_1_1"><i><font color="Green" title="E26">A2</font></i></a>, <a class="ref" href="closure2.html#D6" target="_self" title="CLOSURE2:def.6">Def6</a></i>; <i><font color="Red">:: according to </font></i><a class="ref" href="closure2.html#D10" target="_self" title="CLOSURE2:def.10">CLOSURE2:def 10</a><br/>


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