2/1*3+2/3*5+2/5*7+2/7*9+……+2/97*99
=(3-1)/1*3+(5-3)/3*5+(7-5)/5*7+……+(99-97)/97*99
=1-1/3+1/3-1/5+1/5-1/7+……-1/97+1/97-1/99
=1-1/99
=98/99.
2/1*3+2/3*5+2/5*7+2/7*9+……+2/97*99
=(3-1)/1*3+(5-3)/3*5+(7-5)/5*7+……+(99-97)/97*99
=1-1/3+1/3-1/5+1/5-1/7+……-1/97+1/97-1/99
=1-1/99
=98/99.