" If "2^(n-1)+2^(n+1)=320," then "n" is equal to "

If (1-i)^n = 2^n , then n is equal to

The value of (2^(n) + 2^(n -1))/(2^(n+1) -2^(n)) is equal to

sum_(n=1)^(99) n! (n^2 + n+1) is equal to :

If S_(n)=sum_(r=1)^(n)(1+2+2^(2)+......+2^(r))/(2^(r)), then S_(n) is equal to (a)2^(n)n-1( b) 1-(1)/(2^(n))(c)2n-1+(1)/(2^(n))(d)2^(n)-1