Đáp án:
Giải thích các bước giải:
`a) (-0,25) . 4/17 . ( -3 5/21 ) . ( -7/23)`
`= (-1/4) . 4/17 . (-68/21) . (-7/23)`
`= ( -1 . 4 . ( -68 ) . ( -7 ) )/( 4 . 17 . 21 . 23 )`
`= ( -1 . 4 . ( - 4 ) . 17 . ( -7 ) )/( 4 . 17 . 7 . 3 . 23 )`
`= -4/69`
`b) ( -2/5 ) . 4/15 + ( -3/10 ) . 4/15`
`= 4/15 . ( -2/5 - 3/10 )`
`= 4/15 . ( -4/10 - 3/10 )`
`= 4/15 . ( -7/10 )`
`= ( 4 . ( -7 ))/( 15 . 10 )`
`= -14/75`
`c) 21 - 3 3/4 : ( 3/8 - 1/6 )`
`= 21 - 15/4 : ( 9/24 - 4/24 )`
`= 21 - 15/4 : 5/24`
`= 21 - 15/4 . 24/5`
`= 21 - ( 15 . 24 )/( 4 . 5 )`
`= 21 - 18`
`= 3`
`d) ((-5)/6 + 2/5 ) : 3/8 + ( 4/5 - 11/30 ) : 3/8`
`= ((-5)/6 + 2/5 + 4/5 - 11/30 ) : 3/8`
`= (( -25)/30 + 12/30 + 24/30 - 11/30 ) . 8/3`
`= 0 . 8/3 `
`= 0`
