Then the sum of the first n terms of the sequence {Tn} is sn =1/21+3/22+5/23+...+(2n-1)/2n. ...
Multiply both sides of the equation by 1/2 to get1/2sn =1/22+3/23+5/24+...+(2n-3)/2n+(2n-1)/2.
①-② (dislocation subtraction):1/2sn =1/2+2/22+3+2/24+...+2/2n-(2n-1)/2.
Can be simplified: Sn = 3-(2n+3)/2 n.