=( 1/2)*(3- 1)/ 1*3

=( 1/2)*(3/ 1*3- 1/ 1*3)

=( 1/2)*( 1- 1/3)

1/3*5=( 1/2)*2/3*5

=( 1/2)*(5*3)/3*5

=( 1/2)*(5/3*5-3/3*5)

=( 1/2)*( 1/3- 1/5)

And so on.