Please i don't know how to even BEGIN this question.

A sequence defined as Sn(x) 1 + 2x + 3x^2.....nx^(n-1)

(I assume that the it is a geometric sequence and a is n and r is x? Am i correct?)

By considering (1-x)Sn(x) show that

Sn(x) = 1-x^n/(1-x) - nx^n/(1-x)^2

Obtain the value of

lim (n tends to infinity) {2/3 + 3/2^2 + 4/3^3 + ..... + n/3^(n-1) + 3/2*n/3^n }

What do they mean by limit and i just dont get it! Please help someone!!!