Question

1/3x5+1/5x7+1/7x9+...+1/43x45

Answer 1

=1/3-1/5+1/5-1/7+1/7-1/9+...+1/43-1/45

=1/3-1/45 

Answer 2

1/3-1/5+1/5-1/7+1/7-1/9+...+1/43-1/45

=1/3-1/45

=14/45