${\log ^{\frac{{15}}{2}}} = {\log ^{15}} - {\log ^2} = {\log ^{3 \times 5}} - {\log ^2}$$ = {\log ^3} + {\log ^5} - {\log ^2} = {\log ^3} + 1 - {\log ^2} - {\log ^2}$$ = b + 1 - a - a = b + 1 - 2a$${\log ^5} = 1 - {\log ^2}$ نکته