Đáp án:
`1)`
`-(251xx3+281)+3xx251-(1-281)`
`=-251xx3-281+3xx251-1+281`
`=3xx(251-251)+(281-281)-1`
`=3xx0+0-1`
`=-1`
`2)`
`[2,5xx0,38.(-0,4)]-[-0,125xx3,15xx8]`
`=[(2,5xx(-0,4))xx0,38]-[(-0,125xx8)xx3,15]`
`=(-1)xx0,38-(-1)xx3,15`
`=-0,38+3,15`
`=2,77`
`3)`
`[(-20,83)xx0,2+(-9,17)xx0,2+(-9,17)xx0,2]:[2,47xx0,5-(-3,53)xx0,5]`
`=[0,2xx(-20,83-9,17-9,17)]:[0,5xx(2,47-(-3,53)]`
`=[0,2xx(-39,17)]:[0,5xx6]`
`=(-7,834):3`
`=-(3917)/(1500)`
_______________________________________________________
(bỏ một `-9,17xx0,2`)
`[(-20,83)xx0,2+(-9,17)xx0,2]:[2,47xx0,5-(-3,53)xx0,5]`
`=[0,2xx(-20,83-9,17)]:[0,5xx(2,47-(-3,53)]`
`=[0,2xx(-30)]:[0,5xx6]`
`=(-6):3`
`=-2`
`4)`
`-12,7xx32,6+2,7xx12,8+12,7xx2,6+2,7xx17,2`
`=12,7xx(-32,6+2,6)+2,7xx(12,8+17,2)`
`=12,7xx(-30)+2,7xx30`
`=30xx(-12,7+2,7)`
`=30xx(-10)`
`=-300`
