Find the value `50C_4+sum_(r=1)^6 56-rC_3`.

sum_(r=1)^(6)6C_(r)

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

Find the value of sum_(r = 1)^(10) sum_(s = 1)^(10) tan^(-1) ((r)/(s))

If ,y,z2^(r),2xx3^(r),3xx4^(r)2(2^(n)-1),3*(3^(n)-1),4*(4^(n)-1) Find the value of ,sum_(r=1)^(n)Delta_(r)