\(A=\left\{-2;-1;0;1;2;3;4\right\}\)

\(B=\varnothing\)

\(C=\left\{0;1;2;3;4;5\right\}\)

\(\left(-3;5\right)\cap\left(2;4\right)=\left(-3;5\right)\)

\((-\infty;3]\cap\left[3;5\right]=(-\infty;5]\)

\(\left(-4;2\right)\cap[2;5)=\left(-4;5\right)\)

a) \(A\cap B=\)[\(1;2\)) \(\cup\) (\(3;5\)]

b) \(A\cap B=\)\(\left(-1;0\right)\cup\left(4;5\right)\))

a) (\(-\infty;0\)] \(\cup\left[1;2\right]\cup\) [\(3;+\infty\))

b) (\(-\infty;4\)] \(\cup\) [\(5;+\infty\))

c) \(\left(-2;1\right)\cup\left(3;7\right)\)

d) (\(-1;1\)] \(\cup\) [\(4;5\))

\(A=\left(-3;-1\right)\cup\left(1;2\right)\)

\(B=\left(-1;+\infty\right)\)

\(C=\left(-\infty;2m\right)\)

\(A\cap B=\left(-3;-1\right)\)

Để \(A\cap B\cap C\ne\varnothing\Leftrightarrow2m\ge-1\)

\(\Leftrightarrow m\ge-\dfrac{1}{2}\)

Vậy \(m\ge-\dfrac{1}{2}\) thỏa đề bài

a) (-12; 3] ∩ [-1; 4] = [-1; 3]

b) (4, 7) ∩ (-7; -4) = Ø

c) (2; 3) ∩ [3; 5) = Ø

d) (-∞; 2] ∩ [-2; +∞)= [-2; 2].

Lời giải:

$A\cap B\cap C=A\cap (B\cap C)$

Để tập hợp trên khác rỗng thì trước hết $B\cap C\neq \varnothing$

Điều này xảy ra khi $2m>m\Leftrightarrow m>0$

Khi đó: $B\cap C=(m; 2m)$

$\Rightarrow A\cap B\cap C=((-3;-1)\cup (1;2))\cap (m; 2m)$

$=((-3;-1)\cap (m;2m))\cup ((1;2)\cap (m; 2m))$

$=(1;2)\cap (m; 2m)$ (do $m>0$)

Để $(1;2)\cap (m; 2m)\neq \varnothing$ thì:

\(\left\{\begin{matrix} 2m>1\\ m< 2\end{matrix}\right.\Leftrightarrow m\in (\frac{1}{2};2)\)

Vậy...........

\(\left(-\infty;\dfrac{1}{3}\right)\cap\left(\dfrac{1}{4};+\infty\right)=\left(\dfrac{1}{4};\dfrac{1}{3}\right)\)

\(\left(-\dfrac{11}{2};7\right)\cap\left(-2;\dfrac{27}{2}\right)=\left(-2;7\right)\)

\(\left(0;12\right)\cap[5;+\infty)=[5;12)\)

\(R\cap\left[-1;1\right]=\left[-1;1\right]\)