6分之5减12分之7加20分之9减30分之11加42分之13等于几???????追加200分!!!!!!!!!!!!!!!!!!!!!!!!!!
參考答案:5/6-7/12+9/20-11/30+13/42
=5[1/2-1/3]-7[1/3-1/4]+9[1/4-1/5]-11[1/5-1/6]+13[1/6-1/7]
=5/2-[5/3+7/3]+[7/4+9/4]-[9/5+11/5]+[11/6+13/6]-13/7
=5/2-4+4-4+4-13/7
=5/2-13/7
=9/14
6分之5减12分之7加20分之9减30分之11加42分之13等于几???????追加200分!!!!!!!!!!!!!!!!!!!!!!!!!!
參考答案:5/6-7/12+9/20-11/30+13/42
=5[1/2-1/3]-7[1/3-1/4]+9[1/4-1/5]-11[1/5-1/6]+13[1/6-1/7]
=5/2-[5/3+7/3]+[7/4+9/4]-[9/5+11/5]+[11/6+13/6]-13/7
=5/2-4+4-4+4-13/7
=5/2-13/7
=9/14