Răspuns :
u(1*2)+u(1*2*3)+u(1*2*3*4)+u(1*2*3*4*5)+...+u(1*2*3*4*5*...*2003)=
↓ ↓
acesti termeni contin factorii 2*5=10
=> au ultima cifra 0 !!!
=u(2 + 6 + 4 + 0 +...+ 0 ) = u(12) = 2
↓ ↓
acesti termeni contin factorii 2*5=10
=> au ultima cifra 0 !!!
=u(2 + 6 + 4 + 0 +...+ 0 ) = u(12) = 2