Răspunsuri

2014-10-25T11:00:16+03:00
1. a=2003+2 (2002*2003/2)= 2003+2002*2003=2003*2003=2003²-patrat perfect.
2. a=81+2*81+3*81+...+49*81=81(1+2+3+...+49)=81*(49*50/2)=81*49*25=9² * 7² * 5² = (5*7*9)² -patrat perfect.
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