Cho hai tập hợp A = {x ∈ N| x ≤ 3},B = {x ∈ R | (x² – 4)(x − 1) = 0} . Tìm A U B.

Minh Long

$A=\left\lbrace x\in N\left|x\le3\right\rbrace\right.$

$\Rightarrow A=\left\lbrace0;1;2;3\right\rbrace$

$B=\left\lbrace x\in R\left|(x^2-4\right)\left(x-1\right)=0\right\rbrace$

$\left(x^2-4\right)\left(x-1\right)=0$

$x^2-4=0$ hoặc $x-1=0$

$x^2=4$ hoặc $x=1$

$x=\pm2$ hoặc $x=1$

$\Rightarrow B=\left\lbrace-2;1;2\right\rbrace$

$A\cup B=\left\lbrace0;1;2;3\right\rbrace\cup\left\lbrace-2;1;2\right\rbrace=\left\lbrace-2;0;1;2;3\right\rbrace$.