Question

Calculati ultima cifra a numerelor: 2^2018, 3^2019, 4^2017 si 5^2020.

Answer 1

2^1=2
2^2=4
2^3=8
2^4=...6
2^5=..2
2018:4=504,rest 2=> u.c. (2^2018=4)

3^1=3
3^2=9
3^3=... 7
3^4=...1
2019:4=504,rest 3=> u.c.(3^2019)=7

4^1=4
4^2=...6
2017:2=1008,rest 1=>u.c. (4^2017)=4

orice putere cu baza 5 are ultima cifra egala cu 5