13. (1-log436) (1 – log236)

(1 - log₄36) ⋅ (1 - log₂36) = (1 - log₂²36) ⋅ (1 - log₂36) = (1 - (1/2)log₂36) ⋅ (1 - log₂36) = (1 - (1/2)log₂6²) ⋅ (1 - log₂6²) = (1 - log₂6) ⋅ (1 - 2log₂6) = 1 - 2log₂6 - log₂6 + 2(log₂6)² = 1 - 3log₂6 + 2(log₂6)²

Ответ: $$(1-3log_2 6 + 2(log_2 6)^2$$