[tex]2log_{\frac{1}{4}}8-3log_{\sqrt{3}}9 = \\\\=log_{\frac{1}{4}}8^{2}} -3log_{\sqrt{3}}\sqrt{3}^{4} =\\\\=log_{\frac{1}{4}}64 -3\cdot4 = \\\\=log_{\frac{1}{4}}(\frac{1}{4})^{-3}-12 =\\\\= -3-12 = -15[/tex]
