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aflati volumul cubului cu muchia de (2+3radical5)cm imi dau coroana

Răspuns :

V=(2+3√5)(2+3√5)(2+3√5)=(2+3√5)³=2³+3×2²×3√5+3×2×(3√5)²+(3√5)³=
=8+36√5+270+27×5×√5=278+171√5 cm³

se foloseste formula (a+b)³=a³+3a²b+3ab²+b³