I would love to show ANY effort of my own, but it seams to me that I should use some theorem (of which I have never heard of) in order to attack this problem.
hello there notice that u can seperate this sequence
into two sequences which are both geometric
the first is:x+x^2+x^3+...........+x^n
the second is:1/x +1/x^2+1/x^3+.........1/x^n
now just use the formula for the sum of ageometric sequence