(log(a)c*log(b)c)/(log(a)c+log(b)c)=1
перейдем к единому основанию b
(log(b)c/log(b)a*log(b)c:(log(b)c/log(b)a +log(b)c)=1
log²(b)c/log(b)a :[log(b)c*(1+log(b)a)]/log(b)a=1
log²(b)c/log(b)a *log(b)a/[log(b)c*(1+log(b)a)]=1
log(b)c/(1+log(b)a)=1
log(b)c=1+log(b)a
log(b)c-log(b)a=1
log(b)(c/a)=1
Ответ D