过程答案写清楚!
參考答案:1/42+1/56+1/72+1/90+1/110
=1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)
=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1/6-1/11
=5/66
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过程答案写清楚!
參考答案:1/42+1/56+1/72+1/90+1/110
=1/(6*7)+1/(7*8)+1/(8*9)+1/(9*10)+1/(10*11)
=1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11
=1/6-1/11
=5/66