Uc( 5^2018) = 5
stim ca 5 la orice putere are intotdeauna ultima cifra 5
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Uc( 1 × 2 × 3 × 4 ×...×2018) = 0
5 × 2 = 10; 5 × 4 = 0; 5 × 6 = 0 ...
produsul se termina in cel putin un 0 .
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Uc(x) = Uc( 5 + 0) = 5
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