Q.

The middle term of expansion (10x+x10)10 is

1 C58  
2 C510  
3 C57  
4 C59  

Ans.

(2)

Given expansion is (10x+x10)10

Since, n=10 is even

∴  Middle term=tn2+1=t6

∴  t6=C510(10x)5(x10)5=C510