`sum_(r=1)^(20)(r^2)/((r!(20-r)!)^(2))` is equal to

The value of sum_(r=0)^(20)r(20-r)(^(20)C_(r))^(2) is equal to 400^(39)C_(20) b.400^(40)C_(19) c.400^(39)C_(19) d.400^(38)C_(20)

The value of sum_(r=1)^(15) (r2^(r))/((r+2)!) is equal to

(sum_(r=1)^(n)r^(4))/(sum_(r=1)^(n)r^(2)) is equal to

sum_(r=1)^(n)=(r )/(r^(4)+r^(2)+1) is equal to

sum_(r=1)^(20) r (2r+1)=

sum_(r=1)^(15)(r*2^(r))/((r+2)!) is equal to 1-(2^(m))/(n!) then m is divisible by

sum_(r=0)^(n)((r+2)/(r+1))*""^(n)C_(r) is equal to :

The sum sum_(r=0)^(n)(r+1)(C_(r))^(2) is equal to :

The value of sum_(r = 16)^(30)(r + 2)(r - 3) is equal to :