Binomial Theorem 1 Question 32

34. Find the sum of the series

r=0n(1)rnCr12r+3r22r+7r23r+15r24r upto m terms 

(1985,5M)

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Solution:

  1. r=0n(1)rnCr12r+3r22r+7r23r+15r24r+ upto m terms

=r=0n(1)rnCr12r+r=0n(1)rnCr34r+r=0n(1)rnCr78r+ upto m terms 

=112n+134n+178n+ upto m terms

using r=0n(1)rnCrxr=(1x)n

=12n+14n+18n+ upto m terms

=12n112nm112n=2mn12mn(2n1)



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