Đáp án:
`↓ ↓ ↓ ↓ `
Giải thích các bước giải:
a,
`5/9 - 11/18 = 10/18 - 11/18 = -1/18`
b,
` 1/12 + 3/4 - 5/8 = 2/24 + 18/24 - 15/24 = 20/24 -15/24 = 5/24`
c)
`2/3 . 7/9 + 2/3 . 1/9 - 2/3 . 17/9 = 2/3 . (7/9 + 1/9 - 17/9 ) = 2/3 . 25/9 = 50/27`
d,
`1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56`
`= 1/ 2.3 + 1/ 3.4 + 1/4.5 + 1/ 5.6 + 1/ 6.7 + 1/7.8`
`=1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7 + 1/7 -1/8`
`= 1/2 - 1/8 `
` = 4/8 - 1/8`
` = 3/8 `