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Aratati ca 2+4+6+8+...+2486-1243 este patrat perfect


Răspuns :

2×[2486×(2486+1)÷2]=2×(2486×2487÷2)=2×(6182682÷2)=2×3091341=6182682-1243=6181439÷2=NU ESTE PATRAT PERFECT
[tex]\underbrace{2+4+6+...+2486}_{2(1+2+3+...+1243)}\;-\;1243=\\ =\not2\cdot\frac{1243*1244}{\not2}-1243=1243*1244-1243=1243(1244-1)=1243^2[/tex]