If T_r+1 is the term independent of x in (3x-5/x³)⁸ then r=

The 4^th term of (1-2x)^-1 when x=1/3 is

If x^r occurs in the expansion (x+1/x²)²ⁿ, then its coefficient is:

The sum of the coefficients of (1+2x-4x²)³⁵ is

The number of non zero terms in the expansion of (x+a)¹⁰⁰ + (x-a)¹⁰⁰ is