Question

1/1×2+1/1×2✖️3

1/1×2=1/1-1/2,1/2×3=1/2-1/3,1／3×4＝1／3－1／4……按照规律,求1/2+1/6＋1/12+……1／90的值
过程
急

Answer 1

1/2+1/6＋1/12+……1／90
=1-1/2+1/2-1/3+1/3-1/4+.+1/9-1/10
=1-1/10
=9/10;