giai giùm

Đáp án + Giải thích các bước giải:

 ` Câu 1: `

` a) 1/2 - 5/2 = -4/2 = -2 `

` b) 1/2 + 3/4 = 2/4 + 3/4 = 5/4`

` c) -5/9 + 4/7 = -35/63 + 36/63 = 1/63`

`d) 1/3 + 1/10 = 10/30 + 3/30 = 13/30`

`e) 1/6 - 1/4 = 2/12 - 3/12 = -1/12`

` f) 1/21 - 1/28 = 4/84 - 3/84 = 1/81 `

` g) -2 1/2 - 3 1/4 = -5/2 - 13/4 = -10/4 - 13/4 = -23/4 `

`h) 0,5 - 3/4 = 1/2 - 3/4 = 2/4 - 3/4 = -1/4 `

` i) 1/5 - 0,4 = 1/5 - 4/10 = 2/10 - 4/10 = -2/10 = -1/5`

` j)` Giống câu `c`

` Bài 2: `

` a) 8/10 . 5/11 = 40/110 = 4/11`

` b) 7/5 . 8/3 = 56/15`

` c) 36/35 . 7/54 = 252/1890 = 2/15 `

` d) 5/3 . -3/10 = -15/30 = -1/2 `

` e) - 3/20 : 3/4 = -3/20 . 4/3 = -12/50 = -1/5`

` f) -5/2 : 3/-4 = -5/2 . -4/3 = 20/6 = 10/3 `

` g) - 13/10 : 3/5 = -13/10 . 5/3 = -65/30 = -13/6`

` h) -8/15 . 1 1/4 = -8/15 . 9/4 = -72/60 = -6/5`

` i) 1,25 : (-3,5) = 1,25 . -1/3,5 = -1,25/3,5 = 5/14 `

` j ) 4 1/5 : ( -2 4/5) = 9/4 : -14/5 = 9/4 . -5/14 = -45/ 56`