Question

F={x e N l 2x+5 supra x+1 e N}

Answer 1

2x+5/x+1∈N
x+1/x+1⇒ x+1/2x+2
x+1/2x+5⇒x+1/2x+5
Le scadem si vom obtine:
x+1/-3⇒x+1∈D-3
            x+1∈{1,3,-1,-3}
            x∈{0,2,-2,-4}
            x∈N
Din ambele rezulta x∈{0,2}