Răspunsuri

2014-09-12T12:03:23+03:00
1+3+5+...+21 = n*n
1+3+5+..+2n-1=n*n

2n-1=21
2n=22
n=22:2
n=11

Deci Suma va fi egala cu 11*11=121
2014-09-12T15:09:58+03:00
1+3+5+...+21
1=2·0+1
3=2·1+1....
...
21=2·10+1⇒⇒⇒10+1 · 10+1= 10+1²=121