if (1 + x)^n = (n/0) + (n/1)x + (n/2)x^2 + ........... + (n/n)x^n
show by differentiation that
2(2/n) + (2x3)(n/3) + (3x4)(n/4) + ......... + n(n-1)(n/n) = n(n-1)2^n-2
(what you wrote looks too much like fractions!)
Have you tried this at all? The " " on the right makes me think of differentiating twice (so that the power is reduced to n-2) and then taking x= 1 (so that x+1= 1+ 1= 2). What do you get if you do that on both sides?