Câu 1:
`A ∪ B = (1; +∞)`
`A ∩ B = (2; 3]`
`A` \ `B = (1; 2]`
`B` \ `A = (3; +∞)`
Câu 2:
`A = {x ∈ RR | -1 ≤ x ≤ 2}`
`=> A = [-1; 2]`
`B = {x ∈ RR | x > -1}`
`=> B = (-1; +∞)`
Câu 3:
`overline{P}: "`∃`x ∈ RR: x² ≤ 0`
Câu 4:
`a) x + 1 = 0`
`<=> x = -1`
`b) x - 3 = 0`
`<=> x = 3`
`c) 2x + 1 = 3`
`<=> 2x = 2`
`<=> x = 1`
`d) 3 + x > 0`
`<=> x > -3`
`e) 4 - 2x < 0`
`<=> -2x < -4`
`<=> x > 2`
