Question

rezolvati exercitiul : B= {x cu proprietate x∈ N si 13 < x² - 1 ≤ 90}

Answer 1

13<$x^{2} -1$<90 => 13+1<$x^{2}$<90+1 => 14<$x^{2}$<91 
$3^{2} =9    4^{2}=16$

$9^{2} =81    10^{2} =100$

 x={4,5,6,7,8,9}