Question

Выразите log28 35 через а и в, если log14 7=a, log14 5=в

Answer 1

$log_{28}35= \frac{log_{14}35}{log_{14}28} = \frac{log_{14}(7*5)}{log_{14}(14*14/7)} = \\ \\ = \frac{log_{14}7+log_{14}5}{log_{14}14^2-log_{14}7} = \frac{a+b}{2-a}$