Question

determinati ultima cifra a numarului a=1+2 supra 2+3 supta 3+...+ 2013 supra 2013

Answer 1

a=1+2/2+3/3+......+2013/2013
a=1+1+1+.......+1 ( de 2013 ori)
a=2013
u(a)=u(2013)=3

Answer 2

$A = 1 + \frac{2}{2} + \frac{3}{3}+...+\frac{2013}{2013}$
$A = \underbrace{1 + 1 + 1 + 1 + ... + 1 }_{de\:2013\:ori}$
$A = 1 \cdot 2013$
$u(A) = u(2013) = 3$