Răspuns:
Explicație pas cu pas:
[tex]b)~~\;9^n+9^{n+1}=10\cdot3^{2012}\\ 9^n\cdot(1+9)=10\cdot3^{2012}~\;\;\bigg|{:10}\\ 3^{2n}=3^{2012}\;\Leftrightarrow\;2n=2012\;\Rightarrow \;\boxed{n=1006}[/tex]
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[tex]c)~\;6^n+6^{n+3}=217\cdot6^{55}\\ 6^{n}\cdot(1+6^3)=217\cdot6^{55}~\;\;\big|_{:217}\\ 6^n=6^{55}~\Rightarrow \;\;\;\;\boxed{n=55}[/tex]
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[tex]d)~\;7^{n+1}+7^{n+2}=8\cdot7^{11}\\ 7^{n+1}(1+7)=8\cdot7^{11}~~\;\;\big|{:8}\\ 7^{n+1}=7^{11}\;\Leftrightarrow\;n+1=11\;\Rightarrow \;\boxed{n = 10}[/tex]