calculati
2+4+6+.....+2n


Răspuns :

2+4+6...+ 2n
2(1+2+3+....+n)
2[tex] \frac{n(n+1)}{2} [/tex]
n(n+1)
2+4+6+...+2n=2·(1+2+3+...+n)=2·[tex] \frac{n(n+1)}{2} [/tex]=n·(n+1)=n²+n
atat se poate calcula