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a fost răspuns

Aratati ca numarul a este patrat perfect :
a= (1+2+3+...+99) ×2+100
b=1+2+3+...+50-25×50
c=3+6+9+...+75-75

Răspuns :

Renatemambouko
a= (1+2+3+...+99) ×2+100=99×100/2×2+100=
=99×100+100=100(99+1)=100×100=100²

b=1+2+3+...+50-25×50=50×51/2-25×50=25×51-25×50=25(51-50)=25=5²

c=3+6+9+...+75-75=3(1+2+3+...+25)-75=3×25×26/2-75=975-75=900=30²

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