Difference between revisions of "Proofs to Some Number Theory Facts"

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There are some very useful facts in [[Number Theory]] that have no names.  
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There are some very useful facts in [[Number Theory]] that have no names. If you have a fact, feel free to add it to this page.
  
 
==Fact 1==
 
==Fact 1==
  
 
===Statement===
 
===Statement===
 +
For a prime number <math>p</math>, we have
  
===Proof===
+
<cmath>\dbinom{2p}{p} \equiv 2 \pmod {p}</cmath>
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 2==
 
 
 
===Statement===
 
 
 
===Proof===
 
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 3==
 
 
 
===Statement===
 
 
 
===Proof===
 
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 4==
 
 
 
===Statement===
 
 
 
===Proof===
 
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 5==
 
 
 
===Statement===
 
 
 
===Proof===
 
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 6==
 
 
 
===Statement===
 
 
 
===Proof===
 
 
 
===Uses===
 
 
 
===Examples===
 
 
 
===Problems===
 
 
 
 
 
==Fact 7==
 
 
 
===Statement===
 
  
 
===Proof===
 
===Proof===
 +
We have the congruence
  
===Uses===
+
<cmath>(p-1)! \cdot \dbinom{2p}{p} = 2 \cdot (2p-1) \cdot (2p-2) \cdot \dots \cdot (p+1) \equiv 2 \cdot (p-1)! \equiv -2 \pmod {p}</cmath>
  
===Examples===
+
<cmath>\implies \dbinom{2p}{p} \equiv 2 \pmod {p}</cmath>
  
===Problems===
 
  
==See Also==
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== See Also ==
  
*[[Number Theory]]
+
* [[Number Theory]]
  
 
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Latest revision as of 14:47, 16 May 2025

There are some very useful facts in Number Theory that have no names. If you have a fact, feel free to add it to this page.

Fact 1

Statement

For a prime number $p$, we have

\[\dbinom{2p}{p} \equiv 2 \pmod {p}\]

Proof

We have the congruence

\[(p-1)! \cdot \dbinom{2p}{p} = 2 \cdot (2p-1) \cdot (2p-2) \cdot \dots \cdot (p+1) \equiv 2 \cdot (p-1)! \equiv -2 \pmod {p}\]

\[\implies \dbinom{2p}{p} \equiv 2 \pmod {p}\]


See Also

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