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Lời giải:
$A=9^0+(9+9^2)+(9^3+9^4)+....+(9^{2013}+9^{2014})$
$=1+9(1+9)+9^3(1+9)+....+9^{2013}(1+9)$
$=1+(1+9)(9+9^3+....+9^{2013})$
$=1+10(9+9^3+....+9^{2013})$
$\Rightarrow A$ chia $10$ dư $1$.
a) \(\frac{1}{9}\cdot3^4\cdot3^n=3^7\)
\(\Leftrightarrow\frac{1}{3^2}\cdot3^4\cdot3^n=3^7\)
\(\Leftrightarrow3^{n+2}=3^7\)
\(\Rightarrow n+2=7\)
\(\Rightarrow n=5\)
b) \(\left(2n+1\right)^3=343\)
\(\Leftrightarrow2n+1=7\)
\(\Leftrightarrow2n=6\)
\(\Rightarrow n=3\)
c) \(2\cdot16>2^n>4\)
\(\Leftrightarrow2^5>2^n>2^2\)
\(\Rightarrow5>n>2\)
d) \(n^{45}=n\)
\(\Leftrightarrow n^{45}-n=0\)
\(\Leftrightarrow n\left(n^{44}-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}n=0\\n^{44}-1=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}n=0\\n^{44}=1\end{cases}}\Leftrightarrow\orbr{\begin{cases}n=0\\n=\pm1\end{cases}}\)
e) \(\left(7n-11\right)^3=2^5\cdot5^2+200\)
\(\Leftrightarrow\left(7n-11\right)^3=1000\)
\(\Leftrightarrow7n-11=10\)
\(\Leftrightarrow7n=21\)
\(\Rightarrow n=3\)
(34 . 57 - 92 . 21): 35
= (34 . 57- 34 .21): 35
= 34 . (57 - 21) : 35
= 2916 : 35
= 12
\(\left[\left(6x-72\right):2-84\right].28=5628\)
\(\Rightarrow\left[\left(6x-72\right):2-84\right]=201\)
\(\Rightarrow\left[\left(6x-72\right):2\right]=285\)
\(\Rightarrow6x-72=570\)
\(\Rightarrow6x=642\)
\(\Rightarrow x=107\)
\(A=2+2^2+2^3+2^4+...+2^{10}\)
\(A=\left(2+2^2\right)\left(2^3+2^4\right)+...+\left(2^9+2^{10}\right)\)
\(A=3.2+3.2^3+3.2^5+...+3.2^9\)
\(A=3\left(2+2^3+2^5+...+2^9\right)⋮3\)
Vậy A chia hết cho 3
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