Question

3+6+9+12...+57=
Va roggg mi-l faceți

Answer 1

$3 + 6 + 9 + ... + 57 \\ 3 \times (1 + 2 + 3 + ... + 19) \\ 3 \times \frac{19 \times 20}{2} \\ 3 \times 19 \times 10 \\ 570$

Coroniță pls