tìm stn bt 2n :64=26
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Ta có: \(\frac{2n}{64}=26\)
\(\frac{n}{32}=26\)
\(n=26.32\)
\(n=832\)
\(2^n-64=26\Rightarrow2^n=90\Rightarrow n=log_290\notinℕ\)Đề lag r
2n=16=>2n=24=>n=4
\(4^{2n+1}=64\Rightarrow4^{2n+1}=4^3\)
\(\Rightarrow2n+1=4\Rightarrow n=\frac{3}{2}\)
c)\(6^n=6\Rightarrow n=1\)
k cho mk nha
Bài 1 :
\(A=\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}\)
\(\dfrac{1}{2}xA=\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\)
\(A-\dfrac{1}{2}xA=\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}-\left(\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}+\dfrac{1}{128}\right)\)
\(\dfrac{1}{2}xA=\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}+\dfrac{1}{32}+\dfrac{1}{64}-\dfrac{1}{4}-\dfrac{1}{8}-\dfrac{1}{16}-\dfrac{1}{32}-\dfrac{1}{64}-\dfrac{1}{128}\)
\(\dfrac{1}{2}xA=\dfrac{1}{2}-\dfrac{1}{128}\)
\(\dfrac{1}{2}xA=\dfrac{64}{128}-\dfrac{1}{128}\)
\(\dfrac{1}{2}xA=\dfrac{63}{128}\)
\(A=\dfrac{63}{128}:\dfrac{1}{2}=\dfrac{63}{128}x\dfrac{2}{1}=\dfrac{63}{64}\)
Bài 2 :
Số tự nhiên có 2 chữ số là \(\overline{ab}\left(a;b\inℕ\right)\)
Thêm số 12 vào bên trái số đó :
\(\overline{12ab}=26x\overline{ab}\)
\(1200+10xa+b=26x\left(10xa+b\right)\)
\(1200+10xa+b=260xa+26xb\)
\(260xa-10xa+26xb-b=1200\)
\(250xa+25xb=1200\)
\(25x\left(10xa+b\right)=1200\)
\(10xa+b=48\)
\(\Rightarrow\left\{{}\begin{matrix}a=4\\b=8\end{matrix}\right.\)
Vậy số đó là \(48\)
a) \(2n+7⋮2n+1\)
\(\Rightarrow\left(2n+1\right)+6⋮2n+1\)
\(\Rightarrow6⋮2n+1\)(vì \(2n+1⋮2n+1\))
\(\Rightarrow2n+1\inƯ\left(6\right)\)
\(\Rightarrow2n+1\in\left\{1;2;3;6\right\}\)
\(\Rightarrow\)\(2n\in\left\{0;1;2;5\right\}\)
\(\Rightarrow n\in\left\{0;1\right\}\)
b) \(3m-9⋮3m-1\)
\(\Rightarrow\left(3m-1\right)-8⋮3m-1\)
\(\Rightarrow8⋮3m-1\)(vì \(3m-1⋮3m-1\))
\(\Rightarrow3m-1\inƯ\left(8\right)\)
\(\Rightarrow3m-1\in\left\{1;2;4;8\right\}\)
\(\Rightarrow3m\in\left\{2;3;5;9\right\}\)
\(\Rightarrow m\in\left\{1;3\right\}\)
Hok "tuốt" nha^^
2n:64=26
2n=26.64
2n=1664
n=1664:2
n=832
vậy x=832