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Anshuman prakash Grade: 11
        

If the coefficients of the rth and (r+1)th term in the expansion of (3+7x) raised to power 29 are equal, then r=..?

6 years ago

Answers : (1)

SAGAR SINGH - IIT DELHI
879 Points
										

Dear student,


I will give u a hint here:


Expansion (x+y)n :


(i)        There are (n+1) terms in the expansion.


(ii)        In each term, sum of the indices of ‘x’ and ‘y’ is equal to ‘n’.


(iii)        In any term, the lower suffix of ‘c’ is equal to the index of ‘y’, and the index of x = n-(lower suffix of c).


(iv)             Because  nCr = nCn-r,


    so we have :


nCo = nCn


nC1=nCn-1


nC2=nCn-2 etc.


It follows that the coefficients of terms equidistant from the beginning and the ends are equal.


 



























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Sagar Singh


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sagarsingh24.iitd@gmail.com


























6 years ago
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