\(a,\)\(\frac{x^7}{81}=27\)
\(\Rightarrow x^7=3^3.3^4=3^7\)
\(\Rightarrow x=3\)
\(b,\left(x^2\right)^4=\frac{x^{18}}{x^{10}}\)
\(\Rightarrow x^{18}=x^{10}.x^6\)
\(\Rightarrow x^{18}-x^{16}=0\)
\(\Rightarrow x^{16}\left(x^2-1\right)=0\)
\(\Rightarrow x^{16}\left(x-1\right)\left(x+1\right)=0\)
\(\Rightarrow\hept{\begin{cases}x=0\\x=\pm1\end{cases}}\)
\(\frac{x^7}{81}=27\Rightarrow x^7=27\cdot81=2187\)
\(x^7=2187\Leftrightarrow x^7=3^7\Rightarrow x=3\)
Vậy x=3
\(\left(x^2\right)^4=\frac{x^{18}}{x^{10}}\Leftrightarrow x^8=x^8\Rightarrow x\in R\)
\(\frac{x^7}{81}=27\Leftrightarrow x^7=2187\Leftrightarrow x^7=3^7\Leftrightarrow x=3\)
\(\left(x^2\right)^4=\frac{x^{18}}{x^{10}}\Leftrightarrow x^8=x^8\Leftrightarrow x\)là số gì cũng được trừ số 0
