Question

Srieti elementele multimilor:
A= {x apartine N | 3x mai mic sau egal cu 9} = ........
B= {x apartine Z | |x|=5}=........
C= {x apartine Z | |x| mai mic sau egal cu 2}=.........

Answer 1

$a)~3x \leq 9 \Rightarrow x \leq 3,~x \in N \Rightarrow x \in \{0,1,2,3\}. \\ \\ A=\{0,1,2,3\}. \\ \\ b)~|x|=5 \Rightarrow x \in \{-5,5 \} \\ \\ B=\{-5,5\}. \\ \\ c)~|x| \leq 2 \Rightarrow -2 \leq x \leq 2,~x \in Z \Rightarrow x \in \{-2,-1,0,-1,-2 \}. \\ \\ C= \{-2,-1,0,1,2 \}.$