1/(3*5)+1/(5*7)+1/(7*9)+…1/(103*105)

问题描述:

1/(3*5)+1/(5*7)+1/(7*9)+…1/(103*105)
分子都是1,括号内的两数是分母!

1/(3*5)+1/(5*7)+1/(7*9)+…1/(103*105)
=1/2*(1/3-1/5+1/5-1/7+1/7+...-1/103+1/103-1/105)
=1/2*(1/3-1/105)
=17/105