Cat este A? 5+10+15+......+200 200+................+5 s2=205x40 S2=8200 s=8200:2=4100 4100:41=100 100 este patrat perfect deoarece 100=10 la puterea a doua
5+10+15+...+200=>40 termeni;
Aflam cati termeni are sirul:
200:5=40(termeni)
2s=(5+200)+(10+195)+...+(200+5);
2s=205+205+...+205;
2s=40×205;
2s=8200;
s=8200:2;
s=4100:41;
s=100;
100 este patrat perfect deoarece se scrie ca 10²
