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

The value of sum_(r=0)^(40) r""^(40)C_(r)""^(30)C_(r) is

The value of sum_(r=0)^(10)(r)^(20)C_r is equal to: a. 20(2^(18)+^(19)C_(10)) b. 10(2^(18)+^(19)C_(10)) c. 20(2^(18)+^(19)C_(11)) d. 10(2^(18)+^(19)C_(11))

The value of sum_(r=1)^(n)(-1)^(r-1)((r )/(r+1))*^(n)C_(r ) is

The value of sum_(r=0)^(10) (-1)^(r).4^(10-r)""^(30)C_(r)""^(30-r)C_(10-r) is equal to

The value of ""^(50)C_(4)+sum_(r=1)^(6)""^(56-r)C_(3) is

Prove that sum_(r=0)^(2n)r(.^(2n)C_r)^2=n^(4n)C_(2n) .

Find the sum of sum_(r=1)^n(r^n C_r)/(n C_(r-1) .

The value of sum_(r=1)^n(-1)^(r+1)("^n C r)/(r+1) is equal to a. -1/(n+1) b. 1/n c. 1/(n+1) d. n/(n+1)

Find the sum sum_(k=0)^(10)^(20)C_kdot

The value of sum_(r=0)^(3) ""^(8)C_(r)(""^(5)C_(r+1)-""^(4)C_(r)) is "_____" .