1/2, 2/3, 3/4, 4/5, 5/6, 6/7, 7/8, 8/9, 9/10 ä¸æ¯
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1X1/2+2X1/3+3X1/4+4X1/5+â¦â¦8X1/9+9X1/10
=1/2 + 2/3 + 3/4 + 4/5 + 5/6 + 6/7 + 7/8 + 8/9 + 9/10
=(1-1/2) + (1-1/3) + (1-1/4) + â¦+ ï¼1-1/10)
= 9 - (1/2 + 1/3 + 1/4 + â¦+ 1/10ï¼
= â¦â¦ æ¬å·éè¾¹çè¿æ¯ä¸å¥½ç®åï¼