Question

Rez calculului b=3+6+9...300

Answer 1

Il dam pe 3 factor comun.
3(1+2+3+...+100)=3*(101*100:2)=3*(101*50)=3*5050=15150

Answer 2

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