(1-1/2)*(1-1/3)*(1-1/4)*(1-1/5)*(1-1/6)*…*(1-1/19)*(1-1/20)=
(1-1/2)*(1-1/3)*(1-1/4)*(1-1/5)*(1-1/6)*…*(1-1/19)*(1-1/20)=
(1-1/2)×(1-1/3)×(1-1/4)×(1-1/5)×(1-1/6)×…×(1-1/19)×(1-1/20)=
1-1/2+1/3-1/4+1/5-1/6+1/7-1/8+1/9……+1/19-1/20=?
(1-1/2+1/3-1/4+……+1/19-1/20)/[1/(11×20)+1/(12×19)+……+1/(15×1
1-1/2+1/3-1/4+1/5-1/6…+1/99-1/100)/(1/51+1/52+1/53+…+1/99+1/
1.动脑筋计算:(1+1/2)*(1+1/4)*(1+1/6)*…* (1+1/10)*(1-1/3)*(1-1/5)*
(1+1/2)*(1+1/4)*(1+1/6)*...*(1+1/2008)*(1-1/3)*(1-1/5)*(1-1/
简算:(1+1/3+1/5+1/10+1/15+1/30)÷(1/2+1/4+1/6+1/12+1/20+1/60)=?
(1+1/3+1/5+1/10+1/15+1/30)÷(1/2+1/4+1/6+1/12+1/20+1/60)
1/3+1/6=1/2 1/4+1/12=1/3 1/5+1/20=1/4 …… 1/x+
(1+2/1)(1+4/1)(1+6/1).(1+10/)(1-3/1)(1—5/1).(1-9/1)
1/6【1/4{1/3(1/2X-1)+3}+5】=1