Răspuns:
A={n€N*|0<_n+1<5}
n=1,2,3,4
n+1=>1+1=2
2+1=3
3+1=4
4+1=5
A={2,3,4,5}
B={x|x€N si 13 <x²-1<_99}
x=4,5,6,7,8,9
B={456789}
