Ultima va rog frumos e urgent!


Ultima Va Rog Frumos E Urgent class=

Răspuns :

1+2+...+10=
=10+9+...+1=
=(1•10)*(10:2)+(10:2)=
=(10•5)+5=
=50+5=
=55

1+2+....+n=[n(n+1)]/2

1+2+.....+10=[10(10+1)]/2=5×11=55