The coefficient of the (r+1)th term of (x+ 1x )^ 20 when expanded in the descending powers of x is equal to...

Question

The coefficient of the (r+1)th term of (x+ 1x )^ 20 when expanded in the descending powers of x is equal to the coefficient of the 6th term of (x^2+2+ 1 x^2 )^ 10 when expanded in ascending powers of x. The value of r is

Accepted Answer

(A),(D)

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Solution

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