Question

Se considera multimea a={x e Z| |3x| <21}.Sa se determine numarul de elementi a multimii A

Answer 1

Rezolvarea in atasament

Answer 2

$\it |3x| < 21 \Rightarrow 3|x| <21 |_{:3} \Rightarrow |x| <7 \Rightarrow -7<x<7\ \ \ \ (1) \\ \\ x\in\mathbb{Z} \ \ \ \ \ (2) \\ \\ \\ (1),\ (2) \Rightarrow A=\{-6,\ -5,\ -4,\ -3,\ -2,\ -1,\ 0,\ 1,\ 2,\ 3,\ 4,\ 5,\ 6 \}\Rightarrow \\\ \\ \Rightarrow card(A)=13$