The value of `sum_(r=0)^40 rC(40,r) C(30,r)`

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

The value of sum_(r=0)^(10)r(C(n,r))/(C(n,r-1))=

The value of sum_(r=1)^(10)r.r! is

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)

If C_(r) be the coefficients of x^(r) in (1 + x)^(n) , then the value of sum_(r=0)^(n) (r + 1)^(2) C_(r) , is

The value of sum int_(r=1)^(r=10)rC(10,r) is

The value of C(34,5)+sum_(r=0)^(4)C(38-r,4)=

If a_(n) = sum_(r=0)^(n) (1)/(""^(n)C_(r)) , find the value of sum_(r=0)^(n) (r)/(""^(n)C_(r))