Question

Cho  A ={ x \(\in\) R|| x-1|<3} và B ={ x \(\in\) R|| x+2|>5} hãy tìm A \(\cup\) B, A \(\cap\) B

Answer 1

\(\left|x-1\right|< 3\Leftrightarrow-3< x-1< 3\Leftrightarrow-2< x< 4\)

\(\Rightarrow A=\left(-2;4\right)\)

\(\left|x+2\right|>5\Rightarrow\left[{}\begin{matrix}x+2>5\\x+2< -5\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x>3\\x< -7\end{matrix}\right.\)

\(\Rightarrow B=\left(-\infty;-7\right)\cup\left(3;+\infty\right)\)

\(A\cup B=\left(-\infty;-7\right)\cup\left(-2;+\infty\right)\)

\(A\cap B=\left(3;4\right)\)