If |x| <1/2, then the coefficient of x^r in the expansion of (1+2x) / (1-2x)² is :

If nεN, n is odd then n(n²-1) is divisible by

If the middle term of (1+x)²ⁿ is 1.3.5...(2n-1)k/n! then k=

The general term of (2a-3b)^-1/2 is

The coefficient of x^r in (1+x)²/(1-2x)³ is

49ⁿ+16n+k is divisible by 64 for n?N. Then the numerically least –ve integer value of k is

The coefficient of x^r (0<r<n-1) in the expansion of (x+3)^n-1+(x+3)^n-2. (x+2)+ (x+3)^n-3. (x+2)²+……+(x+2)^n-1 is

ⁿC₀+ⁿC₁+ⁿC₂+………+ⁿC_n =

If the 5^th term is 24 times the 3^rd term in the expansion of (1+x)¹¹ then x=

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