Răspuns: Demonstratia mai jos
Explicație pas cu pas:
Salutare!
[tex]\bf A = 2^{n+2}+2^{n+1} - 2^{n}[/tex]
[tex]\bf A = 2^{n}\cdot(2^{n+2-n}+2^{n+1-n} - 2^{n-n})[/tex]
[tex]\bf A = 2^{n}\cdot(2^{2}+2^{1} - 2^{0})[/tex]
[tex]\bf A = 2^{n}\cdot( 4+2 - 1)[/tex]
[tex]\bf A = 2^{n}\cdot 5 \implies A\:\: \vdots\:\:5[/tex]
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