Question

5. Determinați numărul de elemente ale mulţimii: A = {x€N | 3 ≤ √x ≤ 5}; C = {x€N | 3 ≤ √x ≤ 13}; 10 E = {x€N |2 ​

Answer 1

x∈N

A. 3≤√x≤5 |² => 9≤x≤25

=> A={9,10,11,...,25}

card A=17

B. 11≤√x≤12 |² => 121≤x≤142

=> B={121,122,...,142}

card B=22

C. 3≤√x≤13 |² => 9≤x≤169

=> C={9,10,...,169}

card C=161

D. 2<√x/5<5 | •5 => 10<√x<25 |²

=> 100<x<625

=> D={101,102,...,624}

card D=524