1+2 又1/6+3又1/12+4又1/20+5又1/30+6又1/42+7又1/56+8又1/72

Answer 1

1+2 又1/6+3又1/12+4又1/20+5又1/30+6又1/42+7又1/56+8又1/72
=(1+2+3+....+8)+(1/6+1/12+....+1/72)
=36+[1/(2×3) +1/(3×4)+.....+1/(8×9)]
=36+[1/2 -1/3+1/3-1/4+....+1/8-1/9]
=36+[1/2 -1/9]
=36又7/18