Question

Вычислите log12 1/144-(2/3)^1/2 (27/8)^1/3

Answer 1

$log_{12}\frac{1}{144}-\left(\frac{2}{3}\right)^\frac{1}{2}\cdot\left(\frac{27}{8}\right)^\frac{1}{3}=log_{12}144^{-1}-\left(\frac{2}{3}\right)^\frac{1}{2}\cdot\left(\frac{3^3}{2^3}\right)^\frac{1}{3}\\\\=-log_{12}12^2-\left(\frac{2}{3}\right)^\frac{1}{2}\cdot\frac{3}{2}=-2log_{12}12-\left(\frac{2}{3}\right)^\frac{1}{2}\cdot\left(\frac{2}{3}\right)^{-1}=-2-\left(\frac{2}{3}\right)^{\frac{1}{2}-1}$

$=-2-\left(\frac{2}{3}\right)^{-\frac{1}{2}}=-2-\left(\frac{3}{2}\right)^\frac{1}{2}=-2-\sqrt\frac{3}{2}=-2-\frac{\sqrt3}{\sqrt2}\cdot\frac{\sqrt2}{\sqrt2}=-2-\frac{\sqrt6}{2}\\\\=-\frac{4}{2}-\frac{\sqrt6}{2}=-\frac{4+\sqrt6}{2}$

$-2-\frac{\sqrt6}{2}=-2-0,5\sqrt6\approx-2-0,5\cdot2,45=-3,225$