1/2 log7 36 - log7 14 - 3log7 ∛21 = 1/2 log7 6² - log7 14 - log7 (∛21)³ =
= 1/2 · 2· log7 6 - log7 14 - log7 21 = log7 6 - log7 14 - log7 21 =
= log7 (6:14:21) = log7 (1/49) = log7 (7⁻²) = -2log7 7 = -2·1 = -2
