Răspuns :
1+2+3+...+109=(109×110)/2=109×55
109×55-55×54=55×(109-54)=55×55=55^2 pătrat perfect
rad55^2=55
109×55-55×54=55×(109-54)=55×55=55^2 pătrat perfect
rad55^2=55
N=1 +2+3+...+109-55x54
N=109x110:2-2970
N=11990:2-2970
N=5995-2970
N=3025=55²⇒N este patrat perfect
√N=√55²=55
N=109x110:2-2970
N=11990:2-2970
N=5995-2970
N=3025=55²⇒N este patrat perfect
√N=√55²=55