1. D
2. D
3. D
4.B
5.B
6.A
7.C
8.A
`text{Tự luận:}`
`a) 2/5.``33 1/3-2/5.``8 1/3`
`= 2/5.(33 1/4-8 1/3)`
`= 2/5``.25`
`= 10`
`b) 3/15.√25/81-4/9.√1/16-(2√3)^2`
`= 3/15`.`5/9-4/9.1/4-12`
`= 1/9-1/9-12`
`= -12`
`c) -5/2.√9/25-2^2.|-1/4|`
`= -5/2.3/5-4.1/4`
`= -3/2-1`
`= -5/2`