Đáp án:
Bài `7`:
Ta có: `-9 = - 1 + (-8) = -2 + (-7) = -3 + (-6) = -4 + (-5)= ...`
`⇒ -9/17 = -1/17 + (-8/17)`
`-9/17 = -2/17 + (-7/17)`
`-9/17 = -3/17 + (-6/17)`
`-9/17 = -4/17 + (-5/17)`
....
Bài `8`
`1/2 - 2/3 + 3/4 - 4/5 + 5/6 - 6/7 + 7/8 + 6/7 - 5/6 + 4/5 - 3/4 + 2/3 - 1/2 + 1`
`= (1/2 - 1/2) + (-2/3 +2/3) + (3/4 - 3/4) + (-4/5 + 4/5) + (5/6 - 5/6) + (-6/7 + 6/7) + 7/8 + 1`
`= 0 + 0 + 0 + 0 + 0 + 0 + 7/8 + 1`
`= 7/8 + 8/8`
`= 15/8`
