A
={x apartine N/5x-1≥ 34 si 7x+1 <92}
5x-1≥34 5x≥35 x≥7
7x+1<92 7x<91 x<13
A={7,8,9,10,11,12}
B={x apartineA/x e patrat perfect} ⇒ B={9}
C={x apartine A /2x e
patrat perfect sau 2x +1 e patrat perfect
C={8,12}
pentru ca :
2*8=16 patrat perfect
2*12+1=25 patrat perfect