Thực hiện phép tính: 1/2+3/4-5/6 7/8+-3/5+1/8 2/7+5/7.14/25 1/5-1/5.10/7 6/7+5/7:5-8/9 -7/15:(2/5-5/9)

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1. a, 1/2 + 3/4 – 5/6

   = 6/12 + 9/12 – 10/12

   = 5/12

   b, 7/8+-3/5+1/8

   = (7/8 + 1/8) -3/5

   = 1 -3/5

   = 2/5

   c, 2/7+5/7.14/25

   = 2/7 +2/5

   =10/35 + 14/35

   = 24/35

   d, 1/5 – 1/5 . 10/7

   = 1/5 – 2/7

   = 7/35 – 10/35

   = -3/35

   e, 6/7+5/7:5-8/9

   = 6/7 + 5/35 – 8/9

   = 30/35 + 5/35 – 8/9

   = 1 -8/9 = 1/9

   f) -7/15:(2/5-5/9)

   = -7/15 : (18/45 – 25/45)

   = -7/15 :(-7/45)

   = -7/15 . (-45/7)

   = 3

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2.  `1/2 + 3/4 – 5/6 `

   `=5/4 – 5/6`

   `=5/12 `

   `7/8 + (-3)/5 + 1/8 `

   `=(7/8 + 1/8 ) + (-3)/5 `

   `=1 + (-3)/5 `

   `=2/5

   ` 2/7 + 5/7 . 14/25 `

   `= 2/7 + 2/5 `

   `=24/35 `

   `1/5 – 1/5 . 10/7`

   `=0 . 10/7`

   `=0`

   `6/7 + 5/7 : 5 – 8/9`

   `=6/7 + 5/7 . 1/5 – 8/9`

   `=6/7 + 1/7 – 8/9`

   `=1 – 8/9`

   `=9/9 – 8/9 `

   `=1/9`

   `-7/15  : ( 2/5 – 5/9 )`

   `= -7/15 : (-7)/45 `

   `=-7/15 . (-45)/7`

   `=3`

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