Question

Calculati:
3+6+9+12...+2019
Repede!!☺

Answer 1

$3 + 6 + 9 + 12 + ... + 2019$

$= 3(1 + 2 + 3 + 4 + ... + 673)$

$= 3 \times \frac{673(673 + 1)}{2}$

$= 3 \times \frac{673 \times 674}{2}$

$= 3 \times 673 \times 337$

$= 680403$

Answer 2

3+6+9+...+2019=3(1+2+3+...+673)=3*673*(673+1)/2=3*673*674/2=3*453602/2=

=1360806/2= 680403,   (formula sumei lui Gauss)