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1/(2*3*4)+1/(3*4*5)+……+1/(98*99*100)的解法

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1/(2*3*4)+1/(3*4*5)+……+1/(98*99*100)的解法
1/(2*3*4)+1/(3*4*5)+……+1/(98*99*100)的解法
直接裂项即可:
1/(2*3*4)=[1/(2*3)-1/(3*4)]*1/2
给你一道更难的题!
1/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+.+1/(96×97×98×99)+1/(97×98×99×100)
关键:1/(3×4×5)-1/(4×5×6)=6/(3×4×5×6)-3/(3×4×5×6)=3/(3×4×5×6)
1/(3×4×5×6)=〔1/(3×4×5)-1/(4×5×6)〕/3
1/(1×2×3×4)+1/(2×3×4×5)+1/(3×4×5×6)+.+1/(96×97×98×99)+1/(97×98×99×100)
=1/3〔1/(1×2×3)-1/(2×3×4)+1/(2×3×4)-1/(3×4×5)+1/(3×4×5)-1/(4×5×6)+.+1/(96×97×98)-1/(97×98×99)+1/(97×98×99)-1/(98×99×100)〕
=1/3〔1/(1×2×3)-1/(98×99×100)〕
=163399/2910600