①1/2+1/6+1/12+1/20+1/30+1/42+1/56=②1/1×2+1/2×3+1/3×4+……1/9×10=

来源:学生作业帮助网 编辑:作业帮 时间:2024/06/04 22:19:14
①1/2+1/6+1/12+1/20+1/30+1/42+1/56=②1/1×2+1/2×3+1/3×4+……1/9×10=
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①1/2+1/6+1/12+1/20+1/30+1/42+1/56=②1/1×2+1/2×3+1/3×4+……1/9×10=
①1/2+1/6+1/12+1/20+1/30+1/42+1/56=
②1/1×2+1/2×3+1/3×4+……1/9×10=

①1/2+1/6+1/12+1/20+1/30+1/42+1/56=②1/1×2+1/2×3+1/3×4+……1/9×10=
1/2+1/6+1/12+1/20+1/30+1/42+1/56
= 1/(1*2) + 1/(2*3) + 1/(4*5) + 1/(5*6) + 1/(6*7) +1/(7*8)
= 1-1/2+1/2-1/3+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8
= 1-1/8
= 7/8
1/1×2+1/2×3+1/3×4+……1/9×10
= 1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10
= 1-1/10
= 9/10
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