2 21 3 20这是哪所大学的代号？

求解3/2+7/6+13/12-

3/2+7/6+13/12-21/20+31/30-43/42+57/56+73/72= =[1+(1/2)]+[1+(1/6)]+[1+(1/12)]-[1+(1/20)]+[1+(1/30)]-[1+(1/42)]+[1+(1/56)]+[1+(1/72)] =1+1+1-1+1-1+1+1+(1/2)+(1/6)+(1/12)-(1/20)+(1/30)-(1/42)+(1/56)+(1/72) =4+(1/2)+[(1/2)-(1/3)]+[(1/3)-(1/4)]-[(1/4)-(1/5)]+[(1/5)-(1/6)]-[(1/6)-(1/7)]+[(1/7)-(1/8)]+[(...全部

  3/2+7/6+13/12-21/20+31/30-43/42+57/56+73/72= =[1+(1/2)]+[1+(1/6)]+[1+(1/12)]-[1+(1/20)]+[1+(1/30)]-[1+(1/42)]+[1+(1/56)]+[1+(1/72)] =1+1+1-1+1-1+1+1+(1/2)+(1/6)+(1/12)-(1/20)+(1/30)-(1/42)+(1/56)+(1/72) =4+(1/2)+[(1/2)-(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)] =5-(1/4)-(1/4)+(1/5)+(1/5)-(1/6)-(1/6)+(1/7)+(1/7)-(1/9) =5-(1/2)+(2/5)-(1/3)+(2/7)-(1/9)。
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