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n=64+2*64+3*63+....+49*64 demonstarti ca n=patrat perfect

Răspuns :

n=1·64+2·64+3·64+...+49·64=(1+2+3+...+49)·64=(49+1)(49/2)·64=25·49·64=   
(5·7·8)²=280²⇒n este patrat perfect
N=64(1+2+..+49)
=64·49·50/2
=64·49·25
=8²7²5²
=(8·7·5)(8·7·5)
=280·280
=280²