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Determinati ultima cifra a numarului natural n,unde n=1+1+2+2^2+2^3+...+2^2018

Răspuns :

1+1+2+2²+2³+...+2²⁰¹⁸= 1+2⁰⁺2¹+2²+2³+...+2²⁰¹⁸= 1+2²⁰¹⁹ - 1= 2⁰¹⁹

U(2²⁰¹⁹)=U(2²⁰¹⁶)*U(2³)=U(2⁴)⁵⁰⁴* U(8)= U(16)*U(8)= U(6*8)= U48)= U(8)