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Știind ca x supra y = 3 supra 5, aflați 2x+3y supra 7 x - 4y. DAU COROANA! ​

Răspuns :

Răspuns:

x/y=3/5=>x=3y/5

(2·3y/5+3y)/(7·3y/5-4y)=

(6y/5+⁵⁾3y) / (21y/5-⁵⁾4y)=

(6y/5+15y)/5 / (21y-20y)/5=

(21y/5) / (y/5)=

21y/5·5/y=21