Răspuns :

Răspuns:

a=

[tex] \frac{1 + 24}{2} \times 24 + 13 \times 25 = \frac{25}{2} \times 24 + 13 \times 25= 25 \times 12 + 13 \times 25 = 25(12 + 13) = 25 \times 25[/tex]

=> a este patrat perfect

[tex] \sqrt{a} = \sqrt{25 \times 25} = 25 [/tex]

Targoviste44id

[tex]\it a=1+2+3+\ ...\ +24+13\cdot25=\dfrac{24\cdot25}{2}+13\cdot25=12\cdot25+13\cdot25=\\ \\ =25\cdot(12+13)=25\cdot25=25^2\\ \\ \\ \sqrt{a}=\sqrt{25^2}=25[/tex]

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