Răspunsuri

2014-09-04T11:29:27+03:00
5+10+15+....+200=5x(1+2+3+...40)=5x40x41/2=4100 se aplica sume gauss

9x4100/41=900=30x30 este patrat perfect


2014-09-04T11:33:20+03:00
  9·[5(1+2+3+......+40)]:41=
=9·[5(40·41:2)]:41=
=9·5·20·41:41=
=9·5·20=
=900=30²