1+ 1/1+2+ 1/1+2+3....to n terms.

Answer 1

since 1+2+...+k = k(k+1)/2

Your sum is

n
∑ 2/(k(k+1))
k=1

see what you can do with that.

Note that

1/(k(k+1)) = 1/k - 1/k+1

Answer 2

sir answer this question 2n/n+1

Answer 3

what question? You have the sum correct.