简算：11/30-13/42+15/56-17/72

分类: 作业答案 • 2021-12-19 11:52:12

问题描述：

答

=[5+6]/[5*6]-[6+7]/[6*7]+[7+8]/[7*8]-[8+9]/[8*9]
=4/45

答

11/30-13/42+15/56-17/72
=(1/5+1/6)-(1/6+1/7)+(1/7+1/8)-(1/8+1/9)
=1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9
=1/5-1/9
=4/45

答

11/30-13/42+15/56-17/72
=6/30+5/30-7/42-6/42+8/56+7/56-9/72-8/72
=1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9
=1/5-1/9
=4/45

答

原式=(5+6)/(5*6)-(6+7)/(6*7)+(7+8)/(7*8)-(8+9)/(8*9)
=(1/5+1/6)-(1/6+1/7)+(1/7+1/8)-(1/8+1/9)
=1/5-1/9=4/45