Cho log 2 14 = a . Tính l l o g 49 32 theo a.

\[\begin{array}{*{20}{l}}{a = {{\log }_2}14 = {{\log }_2}2 + {{\log }_2}7 = 1 + {{\log }_2}7 \Rightarrow {{\log }_2}7 = a - 1}\\{{{\log }_{49}}32 = {{\log }_{{7^2}}}{2^5} = \frac{5}{2}{{\log }_7}2 = \frac{5}{2}.\frac{1}{{{{\log }_2}7}} = \frac{5}{{2\left( {a - 1} \right)}}}\end{array}\]