Câu `4`:
`a_)`
`1/2 - (1/3 + 1/4) < x < 1/48 - (1/16 - 1/6)`
`=> 6/12 - 4/12 - 3/12 < x < 1/48 - 3/48 + 8/48`
`=> (-1)/12 < x < 6/48`
`=> -0,08(3) < x < 0,125`
mà `-1 < 0,08(3); 0,125 < 1`
`=> -1 < x < 1` mà `x in mathbb Z`
`=> x = 0`
Vậy `x = 0`
`b_)`
`1/4 + 8/9 <= x/36 < 1 - (3/8 - 5/6)`
`=> 9/36 + 32/36 <= x/36 < 36/36 - 13,5/36 + 30/36`
`=> 41/36 <= x/36 < 52,5/36`
mà `52,5/36 < 53/36`
`=> 41/36 <= x/36 < 53/36`
`=> 41 <= x < 53`
`=> x in {41; 42; 43; ...; 51; 52}`
Vậy `x in {41; 42; 43; ...; 51; 52}`
