a = 31 + 2 + 4 + 6 + .... + 60 a = 31 + 2 ( 1 + 2 + 3 + ... + 30) a = 31 + 2 ( 30 • 31)/ 2 a = 31 + 930 a = 961 a = patrat perfect deoarece √a <=> √961 = 31.

a=31+2+4+6.....+60=31+2(1+2+3+.....+30)=31+2×30×31/2= =31+30×31=31(1+30)=31×31=31² deci este patrat perfect