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hey guys, i have a quesiton on how to add these binomials

 

99c3 + 99c5 + 99c7 + ... + 99c97

 

im decently sure there is a formula for this, but i cannot remember it. help? ty

 Jun 28, 2021
 #1
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Using generating functions, the sum is 2^99.

 Jun 28, 2021
 #2
avatar+118703 
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99C0+99C99=1+1=2

99C1+99C98=99+99 = 198

99C2+99C97=4851+4851=9792

If I add all those together I get   9900

 

So the sum is  2^99 - 9900

 

I think it is anyway.

 Jun 28, 2021
 #3
avatar+26396 
+3

add these binomials

99C3+ 99C5+ 99C7++ 99C97

 

99C0+ 99C1+ 99C2+ 99C3++ 99C97+ 99C98+ 99C99=299 99C1+ 99C3+ 99C5++ 99C97+ 99C99=299299C3+ 99C5+ 99C7++ 99C97=2992 99C1 99C9999C3+ 99C5+ 99C7++ 99C97=29899199C3+ 99C5+ 99C7++ 99C97=298100

 

laugh

 Jun 28, 2021
edited by heureka  Jun 28, 2021
 #4
avatar+118703 
0

Thanks Heureka,  

 

I did not read the question properly.   I didn't notice that it was only odd values of r.

Melody  Jun 28, 2021
 #5
avatar+368 
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thanks heureka!

Badada  Jun 28, 2021

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