Question

Cardinalul multimii A={x apartine N* || x+2 | < sau egal cu 7} este:

Answer 1

lx+2l≤7 <=>
-7≤x+2≤7
-7-2≤x≤7-2
-9≤x≤5
x={-9,-8,-7,-6,-5,-4,...0,1 ,2,3,4,5}=A
cardA=15

Answer 2

$A = \Big\{x\in\mathbb_{N} *\Big| |x+2|\leq 7\Big\} \\ \\ |x+2|\leq7 \\ \\-7\leq x+2\leq 7 \Big|-2 \\ \\ -9\leq x\leq 5 \\ \\ x\in[-9,5] \\ \\ \Rightarrow A = \Big\{1 ; 2 ; 3 ; 4 ; 5\Big\} \Rightarrow \boxed{\text{cardA} = 5}$