Question

小学数学简便计算题2道，，保险起见，，回答好、给额外悬赏分！！5分

1/2+1/6+1/12+1/20+1/30+1/42=(过程、脱式计算）

(1-1/2²)×(1-1/3²)×(1-1/4²)×......(1-1/15²)=(过程、脱式计算）

Answer 1

1/2+1/6+1/12+1/20+1/30+1/42
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7

(1-1/2²)×(1-1/3²)×(1-1/4²)×......(1-1/15²)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)*.....*(1-1/15)(1+1/15)
=1/2*3/2*2/3*4/3*3/4*......*14/15*16/15
=1/2*16/15
=8/15

Answer 2

1/2+1/6+1/12+1/20+1/30+1/42
=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7
=1-1/7
=6/7

Answer 3

这是小学吗？怪怪的。水平比较高啊……

追问

嗯嗯。。是的！！奥赛题！！会不？？