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aratati ca nr. 9x(5+10+15+...+200):41 este patrat perfect



Răspuns :

[tex]9(5+10+15+...+200):41\\ 9*5(1+2+3+...+40):41\\ 45(40*41:2):41\\ 45*820:41\\ 36900:41=900\\\\ \sqrt{900} =30=\ \textgreater \ patrat~perfect. [/tex]