Question

Если
$log_{7}3 = a$
и
$log_{7}5 = b$
то выразите
$log_{7}25 - log_{7}243$
через а и b​

Answer 1

log(a^k) b^l = l/k * log(a) b

log(7) 3 = a

log(7) 5 = b

log(7) 25 - log(7) 243 = log(7) 5² - log(7) 3⁵ = 2 log(7) 5 - 5 log(7) 3 = 2b - 5a