Questions
is equal to
a
(2n)!(n−r)!(n+r)!
b
n!r!(n+r)!
c
n!(n−r)!
d
None of these
detailed solution
Correct option is A
We know,and (1+x)n=C0+C1x+C2x2+…+Crxr+……(i)1+1xn=C0+C11x+C21x2+…+Cr1xr+Cr+11xr+1+Cr+21xr+2…Cn1xn… (ii) on multiplying Eqs. (i) and (ii), equating coefficient of xr in 1xn(1+x)2n orthecoefficientof xn+r in (1+x)2n, we get the value of required expression which is 2nCn+r=(2n)!(n−r)!(n+r)!Talk to our academic expert!
Similar Questions
If the coefficients of P th, ( p + 1)th and (p + 2)th terms in the expansion of (1 + x)n are in AP, then
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