简便运算1/(2*5)+1/(3*5)+1/(8*11)+……+1/(20*23)=这是运用简便运算得出答案,答案是7/46,我想知道做题步骤

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简便运算1/(2*5)+1/(3*5)+1/(8*11)+……+1/(20*23)=这是运用简便运算得出答案,答案是7/46,我想知道做题步骤
简便运算1/(2*5)+1/(3*5)+1/(8*11)+……+1/(20*23)=
这是运用简便运算得出答案,答案是7/46,我想知道做题步骤

简便运算1/(2*5)+1/(3*5)+1/(8*11)+……+1/(20*23)=这是运用简便运算得出答案,答案是7/46,我想知道做题步骤
1/(2*5)+1/(8*5)+1/(8*11)+……+1/(20*23)=
=1/3(1/2-1/5+1/5-1/8+1/8-1/11+...+1/20-1/23)
=1/3(1/2-1/23)
=1/3*21/46
=7/46
你的题目抄错了吧 .