Question

5. Fie A=….. Cardinalul lui A intersectat cu N* este:
a) 9
b) 36
c) 18
d) 6

Answer 1

Răspuns:

a) 9

Explicație pas cu pas:

$- 8 \leqslant \dfrac{2x + 4}{6} < 4 \ \ \Big|\cdot 6\\ - 48 \leqslant 2x + 4 < 24 \ \ \Big|(-4)$

$- 52 \leqslant 2x < 20 \ \ \Big|:2$

$- 26 \leqslant x < 10$

$A \cap \mathbb{{N}^{\ast}} = \Big\{1; 2; 3; 4; 5; 6; 7; 8; 9\Big\}$

$card(A \cap \mathbb{{N}^{\ast}}) = 9$