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Ta có: \(\dfrac{\left(-3\right)^x}{81}=27\)
\(\Leftrightarrow\left(-3\right)^x=2187\)
hay \(x\in\varnothing\)
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\(\Leftrightarrow\dfrac{\left(-3\right)^x}{3^4}=\left(-3\right)^3\\ \Leftrightarrow\left(-3\right)^x=\left(-3\right)^3\cdot\left(-3\right)^4=\left(-3\right)^7\\ \Leftrightarrow x=7\)
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\(a,\Rightarrow\left(x-\dfrac{1}{2}\right)^3=\dfrac{1}{27}=\left(\dfrac{1}{3}\right)^3\\ \Rightarrow x-\dfrac{1}{2}=\dfrac{1}{3}\Rightarrow x=\dfrac{5}{6}\\ b,\Rightarrow\left(\dfrac{3}{2}\right)^{2x-1}:\left(\dfrac{3}{2}\right)^9=\left(\dfrac{3}{2}\right)^4\\ \Rightarrow2x-1-9=4\\ \Rightarrow2x=14\Rightarrow x=7\\ c,\Rightarrow2^{x-1}+2^{x+2}=9\cdot2^5\\ \Rightarrow2^{x-1}\left(1+2^3\right)=9\cdot2^5\\ \Rightarrow2^{x-1}\cdot9=9\cdot2^5\\ \Rightarrow2^{x-1}=2^5\Rightarrow x-1=5\Rightarrow x=6\\ d,\Rightarrow\left(2x+1\right)^2=12+69=81\\ \Rightarrow\left[{}\begin{matrix}2x+1=9\\2x+1=-9\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-5\end{matrix}\right.\)
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a/ \(27^x.9^x=9^{27}:81\)
\(\Leftrightarrow3^{3x}.3^{2x}=3^{54}:3^4\)
\(\Leftrightarrow3^{2x+3x}=3^{50}\)
\(\Leftrightarrow2x+3x=50\)
\(\Leftrightarrow5x=50\)
\(\Leftrightarrow x=10\)
Vậy ...
\(a.27^x.9^x=9^{27}:81\)
\(\left(3^3\right)^x.\left(3^2\right)^x=\left(3^2\right)^{27}:\left(3^2\right)^2\)
\(3^{3x}.3^{2x}=3^{50}\)
\(3^{3x+2x}=3^{50}\)
\(\Rightarrow3x+2x=50\)
\(x\left(3+2\right)=50\)
\(x=50:5=10\)
Vậy\(x=10\)
\(b.\left(\dfrac{12}{25}\right)^x=\left(\dfrac{5}{3}\right)^{-2}-\left(-\dfrac{3}{5}\right)^4\)
\(\left(\dfrac{12}{25}\right)^x=\dfrac{9}{25}-\dfrac{81}{625}\)
\(\left(\dfrac{12}{25}\right)^x=\dfrac{144}{625}\)( Đề sai )
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\(a,\Rightarrow2^3< 2^x\le2^4\Rightarrow x=4\\ b,\Rightarrow3^3< 3^{12}:3^x< 3^5\\ \Rightarrow3^3< 3^{12-x}< 3^5\\ \Rightarrow12-x=4\Rightarrow x=8\)
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Mình cũng không rõ :) , nhưng tại cái đề thầy mình cho Kết quả là 7
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â)\(\dfrac{x^7}{81}=27\Leftrightarrow x^7=27\times81=2187\Leftrightarrow x=3\)
b)\(\dfrac{x^8}{9}=729\Leftrightarrow x^8=729\times9=6561\Leftrightarrow x=3\)
a, \(\dfrac{x^7}{81}=27\)=> x7=27. 81=>x7=2187=>x=3
b, \(\dfrac{x^8}{9}=729\)=>x8=729. 9= 6561=>x=3 hoặc -3
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h) \(5^x+5^{x+2}=650\)
\(\Leftrightarrow5^x+5^x.5^2=650\)
\(\Leftrightarrow5^x\left(1+25\right)=650\)
\(\Leftrightarrow5^x.26=650\)
\(\Leftrightarrow5^x=25\)
\(\Leftrightarrow x=2\)
haizzz,đăng ít thôi,chứ nhìn hoa mắt quá =.=
bây định làm j ở chỗ này vậy??? có j ib ns vs nhao chớ sao ns ở đây
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1: \(\left(\dfrac{1}{16}\right)^x=\left(\dfrac{1}{8}\right)^6\)
\(\Leftrightarrow\left(\dfrac{1}{2}\right)^{4x}=\left(\dfrac{1}{2}\right)^{18}\)
=>4x=18
hay x=9/2
2: \(\left(\dfrac{1}{16}\right)^x=\left(\dfrac{1}{8}\right)^{36}\)
\(\Leftrightarrow\left(\dfrac{1}{2}\right)^{4x}=\left(\dfrac{1}{2}\right)^{108}\)
=>4x=108
hay x=27
3: \(\left(\dfrac{1}{81}\right)^x=\left(\dfrac{1}{27}\right)^4\)
\(\Leftrightarrow\left(\dfrac{1}{3}\right)^{4x}=\left(\dfrac{1}{3}\right)^{12}\)
=>4x=12
hay x=3
\(x\times7\div81=27\)
\(x\times7=27\times81\)
\(x\times7=2187\)
\(x=\dfrac{2187}{7}\)