Logₐ b + logₐ c = logₐ bc
logₐ b - logₐ c = logₐ b/c
log₇ 21/5 - log₇ 3/35 = log₇ 21/5 : 3/35= log₇ 21/5*35/3 = log₇ 7*7 = log₇ 49 = 2
log₅ 75 + log₅ 1/15 = log₅ 75*1/15 = log₅ 5 = 1
log₇ 21/5 - log₇ 3/35 = log₇ 21/5 : 3/35= log₇ 21/5*35/3 = log₇ 7*7 = log₇ 49 = 2
первый и третий одинаковы