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 )
