1+1 1+3 6-3 4-2

-1/2,+1/3,-1/4,+1/5,-1/6,. 1+1 1+3 6-3 4-2 1/1*3+1/2*4+1/3*5+1/4*6+.+1/18*20 1/2-（3/4-3/8）, 1/2+1/4-1/6 , 2/3+（1/2+1/4）, 1/2-（3/4-3/8）,1/2+1/4-1/6 ,2/3+（1/2+1/4）, 2(3^2+1）(3^4+1)(3^6+1)(3^8+1)要简算 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 习题2.8 -2/3+(-1/6)-(-1/4)-1/2 (-2/3)+(-1/6)+1/4-1/2 1+2+3+1+2+3-4+5+6 1/2+1/2*1/3+1/3*1/4+1/4*1/5+1/5*1/6+1/6*1/7+.1/1999*1/2000得多 1、求|1-1/2|+|1/2-1/3|+|1/3-1/4|+|1/4-1/5|+|1/5-1/6|+|1/6-1/7|