âµ1/2²ï¼1/1Ã2,
1/3²ï¼1/2Ã3
1/4²ï¼1/3Ã4
1/5²ï¼1/4Ã5
â¦â¦â¦â¦â¦
1/n²ï¼1/(n-1)·n
â´1/2²+1/2²+1/3²+1/4²+1/5²+â¦+1/n²ï¼1/1Ã2+1/2Ã3+1/3Ã4+1/3Ã4+1/4Ã5+â¦+1/(n-1)·n
=(1-1/2ï¹+ï¹1/2-1/3ï¹+ï¹1/3-1/4ï¹+ï¹1/4-1/5ï¹+â¦+1/(n- 1)-1/n
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+â¦+1/(n-1)-1/n
=1-1/n
=(n-1)/n
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