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<span class="p1">(<span class="default">4 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="newton.html#K12">!</a>  = 
<span class="p1">(<span class="default">4 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="nat_1.html#K2">*</a> <span class="p1">(<span class="default">4 <a href="newton.html#K12">!</a> </span>)</span>
<b>by </b><i><a class="ref" href="newton.html#T21">NEWTON:21</a></i>
<br/>.= 
5 <a href="nat_1.html#K2">*</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default">3 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="nat_1.html#K2">*</a> <span class="p2">(<span class="default">3 <a href="newton.html#K12">!</a> </span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="newton.html#T21">NEWTON:21</a></i>
<br/>.= 
5 <a href="nat_1.html#K2">*</a> <span class="p1">(<span class="default">4 <a href="nat_1.html#K2">*</a> <span class="p2">(<span class="default"><span class="p3">(<span class="default">2 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="nat_1.html#K2">*</a> <span class="p3">(<span class="default">2 <a href="newton.html#K12">!</a> </span>)</span></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="newton.html#T21">NEWTON:21</a></i>
<br/>.= 
120
<b>by </b><i><a class="ref" href="newton.html#T20">NEWTON:20</a></i>
;<br/>
<b>hence </b><a NAME="E2:73"/>
<span class="p1">(<span class="default">4 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="newton.html#K12">!</a>  <a href="hidden.html#R1">=</a> 120
 ;<br/>


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