Răspuns:
a)4+8+12+...+2012
=4(1+2+3+...+503)=507024
b)7+14+21+...+2016=
=7(1+2+3+...+288)=291312
c)3+6+9+...+2013=
=3(1+2+3+...+671)=676368
d)5+10+15+...2015=
=5(1+2+3+...+403)=814060
Am folosit formula lui Gauss
findca prin factorul comun nare cum sal faci
