Q.

The coefficient of the term independent of x in the expansion of (x+1x)10 is equal to

1 10  
2 252  
3 20  
4 256  

Ans.

(2)

General term of expansion (x+1x)10 is

Tr+1=Cr10(x)10-r(1x)r=Cr10x5-r

Term independent of x, means power of x is 0

⇒  5-r=0  ⇒  r=5

Hence,  T5+1=C510=252