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Arata ca nr. a=1+2+3+...+264+265×133 este pătrat perfect.
Ofer coroană!!!


Răspuns :

a = 1 + 2 + 3 + .......+ 264 + 265 x 133

a = 264 x 265 / 2 + 265 x 133

a = 132 x 265 + 265 x 133

a = 265 x ( 132 + 133 )

a = 265 x 265

a = 265² → patrat perfect

a = 1 + 2 + 3 + ... + 264 + 265 × 133

a = ( 264 × 265 : 2 ) + ( 265 × 133 )

a = ( 132 × 265 ) + ( 265 × 133 )

a = 265 × ( 132 + 133 )

a = 265 × 265

a = 265²

→ a = pătrat perfect