Question

afla suma nr consecutive.
a)1+2+3+4+.......+19=
b)1+2+3+4+......+60=
c)2+4+6+8+.....+18=
d)2+4+6+8+.....+60=
e)1+3+5+.......+35=
f)1+3+5+7+......+75=
ma intereseaza regula.multumesc!

Answer 1

formula ( regula )   n x( n+1)/2 adica    ultimul nr x urmatorul : 2

19 x20 : 2