13. (1 - log5(40)) * (1 - log8(40))

(1 - log5(40)) * (1 - log8(40)) = (log5(5) - log5(40)) * (log8(8) - log8(40)) = log5(5/40) * log8(8/40) = log5(1/8) * log8(1/5) = log5(2^(-3)) * log(2^3)(5^(-1)) = -3log5(2) * (-1/3)log2(5) = log5(2) * log2(5) = log5(2) * (1/log5(2)) = 1 Ответ: 1