如题所述
n=4/3-7/12+9/20-11/30+13/42-15/56+17/72
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8+1/8+1/9
=1+1/9
=10/9
nçè´åæ°ä¸º -9/10
=1+1/3-1/3-1/4+1/4+1/5-1/5-1/6+1/6+1/7-1/7-1/8+1/8+1/9
=1+1/9
=10/9
nçè´åæ°ä¸º -9/10
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