Răspuns:
Explicație pas cu pas:3+6+9+.....+369=3(1+2+3+.....100)=3*100*101/2=369*101/2=(369*101)/2=30300/2=15150
[tex]3(1 + 2 + 3 + ......... + 123) = 3 \times \frac{123 \times 124}{2} = 3 \times 123 \times 62 = 22878[/tex]
