Giải các phương trình :$\begin{array}{l}1)\,\,{x^{3 - \log \frac{x}{3}}} = 900\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,3)\,\,{8^{{x^3} - 1}} + {18^{{x^3} - 1}} = {2.27^{{x^3} - 1}}\\2)\,\,{49^{\frac{1}{x}}} - {35^{\frac{1}{x}}} = {25^{\frac{1}{x}}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,4)\,\,{4.3^x}
- {9.2^x} = {5.6^{\frac{x}{2}}}\end{array}$