679. $y=10^{2 x-3}$, i.e. $y=10^{u}$, where $u=2 x-3$.
Solution. $y^{\prime}=10^{\prime \prime} \ln 10 u^{\prime}$ or $y^{\prime}=10^{2 x-3} \ln 10(2 x-3)^{\prime}=$ $=2 \cdot 10^{2 x-3} \ln 10[(4) ; 11,1 ;(1),(2) \S 2]$.