b) 2^1 =2 , 2^2= 4, 2^3= 8, 2^4=16
deci n <4 , n apartine {0,1,2,3}
c) n apartine doar 2
pt ca 3^3= 27 < 57 < 3^4= 81
d)n apartine {0,1,2,3,4,5}
