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Daca a/3=5/b calculați 2ab-28

Răspuns :

a/3 = 5/b

axb = 3 x 5 = 15

2ab - 28 = 2 x 15 - 28 = 30 - 28 = 2

[tex]\it \dfrac{a}{3} = \dfrac{5}{b} \Longrightarrow ab=15\ \ \ (*) \\\;\\ \\\;\\ 2ab-28= 2(ab-14) \stackrel{(*)}{=} 2\cdot (15-14) =2\cdot1=2[/tex]