Question

ajutor!
3+6+9...+297+300=?

Answer 1

3[1+2+3+...+100]
3[50·101]
⇒150·101=15150⇒rezultatul final;

Answer 2

$\displaystyle 3+6+9+...+297+300=3(1+2+3+...+100)= \\ \\ =3 \cdot \frac{100(100+1)}{2} =3 \cdot \frac{100 \cdot 101}{2} =3 \cdot \frac{10100}{2} =3 \cdot 5050=15150$