Cho \(a = {\log _2}3,b = {\log _3}5,c = {\log _7}2...

Câu hỏi: Cho \(a = {\log _2}3,b = {\log _3}5,c = {\log _7}2\). Tính \({\log _{140}}63\) theo \(a, b, c\)

A. \(\frac{{1 + 2ac}}{{1 + 2c + abc}}\)

B. \(\frac{{1 - 2ac}}{{1 - 2c - abc}}\)

C. \(\frac{{1 - 2ac}}{{1 + 2c + abc}}\)

D. \(\frac{{1 + 2ac}}{{1 - 2c + abc}}\)