1/3+1/5+7/30=?1-(7/9+3/4)=?5/7+5/14-3/5=?2/11-(2/3+2/11)=?5/7-X=1/4 一共5题,

(1/3+1/5+1/7)*(1/5+1/7+1/9)-(1/3+1/5+1/7+1/9)*(1/5+1/7)=? 1/1*3+1/3*5+1/5*7+1/7*9+...1/17*19= 1/1*3+1/3*5+1/5*7+1/7*9+1/49*51= 1/1*3+1/3*5+1/5*7+1/7*9+...+1/2007*2009=? 1+3+5+7+9+11=? 1+3+5+7+9= 1+3+5+7+9+.+29= 1+3+5+7+9+.+ =400 1+3+5+7+9+.+2015=? 1+3+5+7+9+.+2005= 1+3+5+7+9+.+119= 计算:1/1×3+1/3×5+1/5×7+1/7×9=? 1/3+1/5+7/30=?1-(7/9+3/4)=?5/7+5/14-3/5=?2/11-(2/3+2/11)=?5/7-X=1/4 一共5题, 1+3又1/6+5又1/12+7又1/20+9又1/30=多少 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9=1-1/9=8/9为什么呢?写出解析. 1+1/1*3+1/3*5+1/5*7+1/7*9+……+1/99*101=? (1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简算(1+1/3+1/5+1/7)*(1/3+1/5+1/7+1/9)-(1+1/3+1/5+1/7+1/9)*(1/3+1/5+1/7) 简便计算 7/12-9/20+11/30-13/42+15/56........................为什么是=1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8?可以说详细点不,