[tex]\it 3|x + 2y \ \ \ \ \ (1)
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Dar,\ \ 3|3x+3y \ \ \ \ (2)
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(1),\ (2) \Rightarrow 3|3x+3y-(x+2y) \Rightarrow 3| 3x+3y-x-2y \Rightarrow 3| 2x+y \ (*)[/tex]
[tex]\it 3|2x + y \ \ \ \ \ (3)
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Dar,\ \ 3|3x+3y \ \ \ \ (4)
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(3), (4) \Rightarrow 3|3x+3y-(2x+y) \Rightarrow3| 3x+3y-2x-y\Rightarrow 3| x+2y \ (**) [/tex]
Din relațiile (*), (**) se obține:
3|x+2y ⇔ 3| 2x+y