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Rosinaella
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Aratati ca x/y=5/6 daca si numai daca (3x+2y) / (2x+5y)=27/40

Răspuns :

Bunicaluiandrei
daca x/y = 5/6
(3x+2y)/2x+5y) = (3x +2·6x/5) / (2x + 5·6x/5) = (3x +12x/5) / (2x+6x) = 27x/5 ·1/8x =
=  27/40
daca (3x+2y)/(2x+5y) = 27/40 
40(3x+2y) = 27(2x+5y)
120x+80y = 54x + 135y
66x = 55y    6x= 5y    x/y = 5/6

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