Question

1乘以2分之3减去2乘以3分之5加3乘以4分之7到51乘以52分之103等于多少

1乘以2分之1加2乘以3分之1加3乘以4分之1加4乘以5分之1加5乘以6分之1加6乘以7分之1等于？

Answer 1

1/(1x2)+1/(2x3)+1/(3x4)+1/(4x5)+1/(5x6)+1/(6x7)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)；去掉小括号后合并化简
=1-1/7
=6/7