Đáp án:
Giải thích các bước giải:
1.
` (-5) . 4 . (-2) . 3 . ( - 25 ) `
` = ( - 20 ) . ( - 6 ) . ( - 25 ) `
` = ( - 120 ) . (-25 ) `
` = 3000 `
` - 47 . 69 + 31 . (-47 ) - ( - 155) + 5 + (-3)^2 `
` = -47 . 69 + 31 . (-47) - (-155) + 5 + 9 `
` = - 47 . ( 69 + 31 ) - (-155 ) + 5 + 9 `
` = -47 . 100 - ( - 155 ) + 5 + 9 `
` = -4700 - (-155) + 5 + 9 `
` = -4545 + 5 + 9 `
` = -4531 `
`c) 27/23 - (-5)/21 - 4/23 + 16/21 + 1/2 `
` = 682/483 - 4/23 + 16/21 + 1/2 `
` = 26/21 + 16/21 + 1/2 `
` = 2 + 1/2 `
` = 5/2 `
`d) -8/9 + 1/9 . 2/9 + 1/9 . 7/9 `
` = -8/9 + 1/9 + 1/7 `
` = -40/63 `
2.
` x - 105 : 3 = -23 `
` x - 35 = -23 `
` x = -23 + 35 `
` x = 12 `
vậy ` x = 12 `
` x -1/2 = 3/4 `
` x = 3/4 + 1/2 `
` x = 3/4 + 2/4 `
` x = 5/4`
vậy ` x = 5/4 `
` 1/2x - 1/4 = -1/2 `
` 1/2x = -1/2 + 1/4 `
` 1/2x = -1/4 `
` x = -1/4 : 1/2 `
` x = -1/2 `
vậy ` x = -1/2 `
3.
`a)` ` -14/21 = -2/3 `
` 60/-72 = -5/6 `
` -2/3 = -4/6 `
vì ` -4 > -5 `
suy ra ` -14/21 > 60/-72 `
`b)` ` 5/6 + 1/6 ≤x≤13/4 + 14/8 `
` 6/6 ≤x≤ 26/8 + 14/8 `
` 1≤x≤5 `
vậy ` x \in{1;2;3;4;5 } `