(1+1/5)*(1-1/9)*(1+1/6)*(1-1/6)*(1+1/7)*(1-1/7)*...*(1+1/20)*(1-1/20)用简便算法怎样算?

1*1*1*5*5*5*9*9*9+1*1*1*1等于 ((1/2)-1)*((1/3)-1)*((1/4)-1)*((1/5)-1)*((1/6)-1)*((1/7)-1)*((1/8)-1)*((1/9)-1)*((1/10)-1) 1/5*1/9+1/9*1/13+1/13*1/17+.1/101*1/105 1+1+1+1+11+1+1+1+1+1+1+1+5+5+5+8+9等于几 9*(1-1/2)*(1-1/3)*(1-1/4)*(1-1/5)*(1-1/6)*(1-1/7)*(1-1/8)*(1-1/9)怎样简便计算 （1+1/2)*(1+1/4)*.*(1+1/10)*(1-1/3)*(1-1/5)*.(1-1/9)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 1*1/5+1/5*1/9 1*1/5+1/5*1/9+1/9*1/13+1/13*1/17 计算 /1/3-1/2/+/1/4-1/3/+/1/5-1/4/+.+/1/10-1/9/ |1/3-1/2|+|1/4-1/3|+|1/5-1/4|+...+|1/10-1/9| 1+1-1+1-1+1-1+1-1+9-1-1-1-1-1-1-1-1等于几 (1/3+1/5+1/7)*(1/5+1/7+1/9)-(1/3+1/5+1/7+1/9)*(1/5+1/7)=? 简算:1/1*3+1/3*5+1/5*7+1/7*9+1/9*11 1*5/1+5*9/1+9*13/1+13*17/1+17*21/1 1/1*5+1/5*9+1/9*13+1/13*17+1/17*21 (1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1 1/1*3+1/3*5+1/5*7+1/7*9+1/9*11 (1*3)/1+(3*5)/1+(5*7)/1+(7*9)/1+(9*11)/1