3) 1 log7 36 - log7 14 – 3 log73√21; 2 3

Решение:

$$\frac{1}{2} log_7 36 - log_7 14 - 3log_7 \sqrt[3]{21} = log_7 36^{\frac{1}{2}} - log_7 14 - log_7 (21^{\frac{1}{3}})^3 = log_7 6 - log_7 14 - log_7 21 = log_7 \frac{6}{14} - log_7 21 = log_7 \frac{3}{7} - log_7 21 = log_7 \frac{\frac{3}{7}}{21} = log_7 \frac{3}{7 \cdot 21} = log_7 \frac{3}{7 \cdot 7 \cdot 3} = log_7 \frac{1}{49} = log_7 7^{-2} = -2$$

Ответ: -2