Răspuns :
U(3^2017)=U(3^4+504x1)=U(3^1)=3
=>U(3^2017)=3
......................
U3¹ = 3
U3² = 9
U3³ = 7
U3⁴ = 1
U3⁵ = 3
Ultima cifra se repeta la un interval de 4
2017 : 4 = 504 rest 1
U3²⁰¹⁷ = 3
U(3^2017)=U(3^4+504x1)=U(3^1)=3
=>U(3^2017)=3
......................
U3¹ = 3
U3² = 9
U3³ = 7
U3⁴ = 1
U3⁵ = 3
Ultima cifra se repeta la un interval de 4
2017 : 4 = 504 rest 1
U3²⁰¹⁷ = 3