Đề bài
Cho các tập hợp: \(A = \left[ { - 1;2} \right),B = \left( { - \infty ;1} \right]\)
Xác định \(A \cap B;A \cup B;A\backslash B;B\backslash A;\mathbb{R}\backslash B;{C_\mathbb{R}}A.\)
Lời giải chi tiết
a)
Vậy \(A \cap B = \left\{ {x \in \mathbb{R}\left| { - 1 \le x < 2,x \le 1} \right.} \right\} = \left\{ {x \in \mathbb{R}\left| { - 1 \le x \le 1} \right.} \right\} = \left[ { - 1;1} \right]\)
b)
Vậy \(A \cup B = \left\{ {x \in \mathbb{R}\left| { - 1 \le x < 2,x \le 1} \right.} \right\} = \left\{ {x \in \mathbb{R}\left| {x < 2} \right.} \right\} = \left( { - \infty ;2} \right)\)
c)
Vậy \(A\backslash B = \left\{ {x \in \mathbb{R}\left| { - 1 \le x < 2} \right.} \right\}\backslash \left\{ {x \in \mathbb{R}\left| {x \le 1} \right.} \right\} = \left\{ {x \in \mathbb{R}\left| {1 < x < 2} \right.} \right\} = \left( {1;2} \right)\)
d)
\(B\backslash A = \left\{ {x \in \mathbb{R}\left| {x \le 1} \right.} \right\}\backslash \left\{ {x \in \mathbb{R}\left| { - 1 \le x < 2} \right.} \right\} = \left\{ {x \in \mathbb{R}\left| {x < - 1} \right.} \right\} = \left( { - \infty ; - 1} \right)\)
e)
Vậy \(\mathbb{R}\backslash B = \mathbb{R}\backslash \left\{ {x \in \mathbb{R}\left| {x \le 1} \right.} \right\} = \left\{ {x \in \mathbb{R}\left| {x > 1} \right.} \right\} = \left( {1; + \infty } \right)\)
g)
Vậy \({C_\mathbb{R}}A = \mathbb{R}\backslash \left\{ {x \in \mathbb{R}\left| { - 1 \le x < 2} \right.} \right\} = \{ x \in \mathbb{R}\left| {x < - 1} \right.\) hoặc \(x \ge 2\} = \left( { - \infty ; - 1} \right) \cup \left[ {2; + \infty } \right)\)