问题描述：
计算
1/1*3+1/3*5+1/5*7+...+1/2007+2009
找规律.
1.( ),18,15,( ),9,6
2.4/67,2/15,16/53,16/23,64/39,( ),( )
答
1/1*3+1/3*5+1/5*7+...+1/2007+2009 =[1-1/3+1/3-1/5+1/5-1/7+.+1/2007-1/2009]/2 =(1-1/2009)/2 =1004/2009 找规律.1.( 21 ),18,15,( 12 ),9,6 2.4/67,2/15,16/53,16/23,64/39,( 4 ),( 256/25 )