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[tex] 3^{n+1} × [tex] 2^{2n+1} +[tex] 3^{n+2} ×
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[/tex][tex] 4^{n+1} (divizibil) 42
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Tex 3n1 Tex 22n1 Tex 3n2 Tex Tex Textex 4n1 Divizibil 42 Tex class=

Răspuns :

[tex]3^{n+1}\cdot 2^{2n+1}+3^{n+2}\cdot 4^{n+1}=\\ 3^n\cdot3\cdot4^n\cdot 2+3^n\cdot9\cdot4^n\cdot4=\\ 12^n\cdot 6+12^n\cdot36=\\ 12^n(6+36)=\\ 12^n\cdot 42\vdots\ 42\forall n\in N[/tex]