b) \(\dfrac{9^4.27^5}{3^{11}}\)
\(=\dfrac{\left(3^2\right)^4.\left(3^3\right)^5}{3^{11}}\)
\(=\dfrac{3^8.3^{15}}{3^{11}}\)
\(=\dfrac{3^{23}}{3^{11}}\)
\(=3^{12}\)
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c: Ta có: \(5^{x-3}=25\)
\(\Leftrightarrow x-3=2\)
hay x=5
d: Ta có: \(\left(-8\right)^x=\dfrac{1}{64}\)
\(\Leftrightarrow8^x=\dfrac{1}{8^2}\)
hay x=-2
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