Question

B={x e N | -5 ≤ -√x ≤ -2}
C={x e N | 27 ≤ 3x² ≤ 147}​

Answer 1

Explicație pas cu pas:

$- 5 \leqslant - \sqrt{x} \leqslant - 2$

$2 \leqslant \sqrt{x} \leqslant 5$

${2}^{2} \leqslant {( \sqrt{x} )}^{2} \leqslant {5}^{2} \iff 4 \leqslant x \leqslant 25$

=> B = {4, 5, 6, ..., 23, 24, 25}

$27 \leqslant 3 {x}^{2} \leqslant 147$

$9 \leqslant {x}^{2} \leqslant 49$

${3}^{2} \leqslant {x}^{2} \leqslant {7}^{2} \iff 3 \leqslant x \leqslant 7$

=> C = {3, 4, 5, 6, 7}