1/1*3+1/3*5+1/5*7+...+1/17*19
问题描述：
1/1*3+1/3*5+1/5*7+...+1/17*19
答
1/1*3+1/3*5+1/5*7+...+1/17*19
=1/2 x (1/1 -1/3 +1/3 -1/5 +...+1/17 -1/19)
=1/2 x (1 - 1/19)
=9/19