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A=1+3+3^2+3^3+3^4+...+3^99
E urgent!


Răspuns :

ce ai tu acolo mai poate fi scris si:
A=3^0+3^1+3^2+...+3^99 /*3
3A=3^1+3^2+3^3+..+3^99+3^100
(le scazi, si vor disparea f multi termeni)
2A=3^100-3^0
A=(3^100-1)/2
Coroana?
A=1+3+3^2+3^3+3^4+.....+3^99
2A=3+3^2+3^3+3^4+.....+3^99+3^100
2A-A=3^100-1
A=3^100-1
U(3^100)=U(3^4)^25=U(1x25)=5
U=ultima cifra