Question

Care este ultima cifra a puterii de la rezultatul 7²°°°+5¹⁹⁹⁹?

Answer 1

u($7^{123}$+$5^{1999}$)
u(7la1)=7
u(7la2)=9
u(7la3)=3
u(7la4)=1
2000:4=500
2000=4*500
u(7la4*500)=u((7la4)la500)=u(1la500)=u(1)

u(5la1999)
u(5la1)=5
u(5la2)=5
u(5la3)=5
u(5la1999)=u(5)
u($7^{2000} + 5^{1999}$)=u(1+5)=u(6)