Question

4+8+12+..+204
d)
3+6+9+... + 153.
Cum se poate simplifica

Answer 1

 

$\displaystyle\bf\\4+8+12+...+204=4(1+2+3+...+51)=4\times\frac{51(51+1)}{2}=\\\\ =4\times\frac{51\times52}{2}=4\times51\times26=4\times1326=5304\\\\\\3+6+9+...+153=3(1+2+3+...+51)=3\times\frac{51(51+1)}{2}=\\\\ =3\times\frac{51\times52}{2}=3\times51\times26=3\times1326=3978$